MXPA99003757A

MXPA99003757A - A method for processing refractory auriferous sulfide ores involving preparation of a sulfide concentrate

Info

Publication number: MXPA99003757A
Application number: MXPA/A/1999/003757A
Authority: MX
Inventors: L Simmons Gary; C Gathje John
Original assignee: Newmont Gold Company
Priority date: 1996-10-23
Filing date: 1999-04-22
Publication date: 1999-10-14

Abstract

A method is disclosed for processing a gold-bearing refractory sulfide ore (102) by maintaining the ore in a substantially oxygen free environment, preferably beginning with comminution (104) of the ore and ending after a desired final concentrate, enriched in sulfide minerals, is obtained by flotation (112). In one embodiment, nitrogen gas (110) is used to prevent contact between the ore and air during comminution of the ore (108) and during flotation operations (114). This invention recognizes that gold in refractory sulfide ores primarily occurs in refractory auriferous sulfides, which are typically the most difficult sulfide species in the ores to float. By reducing the exposure of those refractory auriferous sulfides to oxygen gas during flotation, flotation recovery is enhanced in the form of a flotation concentrate (116). A flotation tail (118) is also obtained from the process.

Description

METHOD FOR PROCESSING MINERALS OF SULFURO AURÍFERO REFRACTORY THAT IMPLIES THE PREPARATION OF THE CONCENTRATE OF SULFIDE FIELD OF THE INVENTION The present invention relates to a method for processing refractory sulfide minerals bearing gold, including refractory gold sulphides, to facilitate the recovery of gold. In particular, the present invention relates to the flotation processing of refractory sulfide ores in a form that reduces the problems associated with the conventional flotation of refractory gold sulphides in the ores to produce a concentrate of ore that is concentrated in the refractory auriferous sulfides. and, consequently, also in the gold within the refractory auriferous sulfides.

BACKGROUND OF THE INVENTION Significant amounts of gold are found in minerals that are usually referred to as refractory sulfides. The gold in these minerals is usually referred to as refractory, since it can not be recovered through direct cyanidation. That is, since the refractory gold is bonded in the crystalline structure of the sulfide mineral and is, therefore, not available for recovery through traditional gold recovery techniques, such as direct cyanidation of the mineral Therefore, these refractory sulfide minerals are commonly treated to chemically destroy the crystalline structure of the sulfide mineral where the gold is located and to release the gold for dissolution, such as through cyanidation, during subsequent gold recovery operations One technique to destroy the crystalline structure of the sulfide mineral is to subject the ore to an oxidizing treatment to oxidize sulfur sulfur, thus releasing the gold for the subsequent recovery A method to oxidatively treat a refractory sulfide mineral is pressure oxidation, where a slurry of ore is subjected to oxygen gas in an autoclave at elevated temperature and pressure to decompose the sulfide ore, releasing the gold for the Subsequent recovery Other methods of oxidant treatment in cluyen calcining and bio-oxidation of the mineral in the presence of air or oxygen gas The treatment of complete minerals through oxidation by pressure or oxidizing calcination is expensive Part of the expense is due to the energy consumed to heat the material of gangue that has no gold in the complete mineral, and especially in the energy required to heat the water where the gangue material is formed as a slurry in the case of pressure oxidation. Also, the process equipment to treat an entire ore must be sized to adapt the production of the gangue material, in addition to the production of refractory auriferous sulphides, thus adding significantly to the cost of the process equipment. In addition, lateral reactions may occur which imply that the gangue material may dangerously affect the oxidizing treatment or may produce hazardous materials that require special handling. One way to reduce the high energy and high costs of the process equipment associated with the oxidative treatment of all ore, as well as the potential problems associated with side reactions, could be removed the ore material of the ore before oxidizing treatment. For example , a method that has been used to remove the gangue material from refractory sulfide minerals is flotation. In flotation, the air is bubbled through a slurry of mineral particles, which have been treated with reagents and the mineral particles that are less hydrophilic tend to bind and elevate with the air bubbles, thus allowing the separation of the mineral into two fractions The flotation has been used to prepare sulphide mineral concentrates from refractory sulfide minerals in an attempt to concentrate the gold in the flotation concentrate, thus avoiding The expense of processing the gangue in a subsequent oxidant treatment A problem with the flotation of refractory sulfide ores, however, is that a significant amount of refractory gold usually reports an erroneous flotation fraction, even though a high percentage of sulfide minerals is recovered in the concentrate There is a significant need for an improved method to process refractory sulfide minerals that avoids the high costs associated with the oxidative treatment of complete minerals without the significant loss of refractory gold associated with the concentration of sulfide minerals through conventional flotation.

COMPENDIUM OF THE INVENTION The present invention relates to a method for processing refractory sulfide minerals to facilitate the recovery of gold without the burden of oxidation by pressure or calcination of a complete mineral and without the substantial loss of gold value associated with the preparation of a concentrate. Ore Through Conventional Flotation With the present invention it has been found that much of the refractory gold in the refractory sulfide ores is contained in sulfur species referred to herein as refractory auriferous sulfides. Although these sulfide species may represent only a small fraction of sulfides in a refractory sulfide mineral typically contain a greater part of the refractory gold. As used herein, refractory gold sulfides are sulfides containing gold ie they are willing to direct cyanidation, except through the destruction of the base structure of the sulfide ore, which is usually achieved through the oxidation of the refractory auriferous sulfide Typically, these refractory auriferous sulphides are arsenic ferrous gold sulphides, which have a composition according to the formula FexAsySz * Au, where x, y, z are in any relative proportion The gold contained in the refractory gold sulfides is in a solid solution in the base structure of the sulfide mineral and is refractory gold since it is not willing to recover through the direct cyanidation, except through the destruction of the base structure of the sulfide mineral, which is typically achieved through the oxidation of refractory gold sulfides. Said gold in solid solution is sometimes also referred to as atomic gold or gold It has been found that the largest occurrences of refractory gold in sulphide minerals refra These occur in these refractory auriferous sulfides. Little, if any, refractory gold occurs in other sulfide species that contain classically known pure iron sulfide, such as pyrite (FeS2), marcasite (FeS2), and pyrrhotite (Fe (! X) S, x varying from 0 to 0 17) This distinction is important since traditional flotation, which involves the use of air as a flotation gas, is usually effective to recover a large fraction of the sulfide species that contains more traditionally recognized iron It has been found that with the present invention, however, floating Traditionally, it is not effective for the flotation of refractory gold sulphides, which contain the majority of refractory gold. Therefore, it is usually possible for traditional flotation to recover a high percentage of sulfide minerals in the concentrate, and at the same time experience a low recovery in the refractory gold concentrate This is due to an unacceptably large fraction of the refractory gold sulfides, which contain most of the refractory gold, reported to the flotation tails Refractory gold sulfides should not be confused with sulfides non-refractory Gold in non-refractory sulfides occurs as particulate gold that is willing to direct cyanidation without destruction of the base structure of the sulfide mineral. This non-refractory, particulate gold can be exposed, to the extent necessary, to cyanidation direct through mechanical processing, such as crushing to a size or of very fine particle, before directing the cyanidation However, it should be noted that although the gold of the non-refractory sulfides can be recovered through direct cyanidationIt is not always economical to do this. For example, particulate gold inclusions are usually found in copper and other base metal sulfides. Copper in many copper sulfides, however, has varying degrees of solubility through copper. direct cyanidation Therefore, the consumption of cyanide becomes prohibitively large for the economic extraction of gold to through direct cyanidation due to the dissolution of concurrent copper cyanide It has been found with the present invention that the air which is used as the flotation gas in the conventional flotation dangerously affects the flotation of refractory auriferous sulfides According to the present invention a significantly improved flotation performance can be obtained by keeping the ore in a substantially air-free environment until a desired final flotation concentrate has been obtained. It is believed that the refractory auriferous sulfides are particularly reactive, susceptible to surface oxidation when the presence is present. of oxygen gas such as if air is present It is this reactivity which can cause a significant fraction of the refractory auriferous sulfides that is depressed during conventional flotation in air. Using a flotation gas that is deficient in oxygen gas in relation to the However, the problems associated with the use of air can be reduced. This results in an increased recovery of refractory gold sulphides in the concentrate and correspondingly an increase in the recovery of the refractory gold in the concentrate. It is also believed that the presence of oxygen promotes the increased galvanic interaction that tends to depress the gold sulfides refracting them during flotation In one embodiment the refractory gold sulfides in a refractory sulfide mineral are maintained in an environment that is substantially free of oxygen beginning with the crushing of the ore and ending with the recovery of a desired final concentrate that is rich in refractory gold sulfides. An oxygen deficient gas can be introduced before or during crushing to displace any air that may be present in the ore feed and prevent air from entering during crushing Oxygen in air that might otherwise be present during crushing, thus, it is not allowed to oxidize surfaces Recently exposed refractory gold sulphides created during grinding Although grinding in an oxygen deficient gas atmosphere is preferred, an alternative to reduce the damaging effects of oxygen is to seal the entire grinding process to prevent air from entering the process during the crushing With this alternative, alone The oxygen initially in the feed for crushing will be present, so that the damage to refractory gold sulphides will be limited. In addition to reducing oxygen levels during crushing and flotation, the use of an oxygen deficient gas tends to reduce the galvanic interaction, with a corresponding increase in the flotation capacity of the refractory auriferous sulfides In one embodiment, the galvanic interaction is also reduced by reducing the amount of iron introduced in the system and / or removing the iron from the system. Iron contamination in the system system can be reduced using grinding media made of stainless steel or a steel hardened with chrome or nickel, instead of normal mild steel, and / or using a non-metallic liner for the grinding equipment. The iron can be removed from the system before flotation through magnetic separation It has been found that the reduction of the galvanic interaction can significantly improve the recovery of refractory gold sulfides during flotation, especially when the flotation is conducted with a deficient oxygen flotation gas. Possible sources of oxygen deficient gas they include by-product gas from an oxygen plant, a dedicated nitrogen plant, combustion exhaust gases, or on-site supply of compressed or liquefied gases. In a manner to reduce the consumption of the oxygen deficient gas, the Flotation is recirculated in the flotation operation When a floc gas is used oxygen deficient composition according to the present invention, it has been found that the adjustment of other flotation operation parameters is unusually important to maximize flotation performance. In this regard, it has been found that the flotation must be operated at an acid pH, preferably below about 6. Also, the use of an activator containing lead significantly improves flotation performance, as well as the use of deoxygenated water during crushing and flotation. These additional improvements are particularly important since, as noted, it has been found that refractory gold is usually very much associated with refractory gold sulfides, which are the mineralogical / morphological sulphide species that are generally the hardest to float. For example, a flotation improvement that increases the recovery of sulfide ore by only one percentage point can increase the recovery of the refractory gold in the concentrate through a proportionally larger amount. This is because the increasing sulfur ore particles which tend to float with each improvement include those likely to contain significant amounts of refractory gold. Conversely, sulphide minerals that are easier to float such as pyrite usually contain little or no gold. Another mode according to this invention includes a leaching of flotation tails to recover gold not r effractory that can remain in the flotation tail Many minerals contain both refractory and non-refractory gold Most non-refractory gold, if contained in non-refractory sulfides will float during flotation along with refractory gold sulfides Other non-refractory gold, such as that associated with oxidized mineral species, can report to the flotation tail, from which this non-refractory gold can be recovered through cyanidation of the flotation tail For some sulfide minerals, the non-refractory gold in the tail of flotation can be a significant amount of gold A major advantage of the present invention is that the flotation tail is relatively clear of sulfide minerals It is important to effect leaching with tail cyanide due to the significant loss of cyanide that could occur if amounts important sulfur minerals were present in the flotation tails In a further embodiment according to the present invention a significant operational improvement is obtained by performing an intermediate regrinding operation between two flotation stages or in a sand fraction from the first flotation tail after the separation by size to remove the particles This allows a coarser grinding to be used for an initial flotation stage to recover a significant amount of sulfide species in the ore including a significant amount of the refractory gold sulfides. The regrind allows the additional release of Sulfide blocked in medium-sized particles A very fine grinding may be required in this regrind to effectively release refractory gold sulfides that can be blocked in medium-sized particles since the refractory auriferous sulphides tend to be fine-grained in character. in stages it could not be possible with conventional air flotation due to the harmful effects of oxygen on refractory gold sulfides during conventional milling and flotation In another embodiment of the present invention, the flotation operation which is conducted substantially in the absence of oxygen gas, is combined with oxidizing treatment to decompose the refractory gold sulfides, releasing refractory gold for a possible subsequent solution using a gold lixiviant, such as a cyanide The preferred oxidizing treatment is pressure oxidation, although other oxidizing treatment such as oxidizing calcination or bio-oxidation may be used. Such oxidizing treatment usually requires a source of purified oxygen gas, which is usually produced through of the separation of air in an oxygen plant A by-product gas from said oxygen plant is deficient in oxygen gas and rich in nitrogen gas. The by-product gas, therefore, is an ideal source of gas to be used during the crushing and / or flotation of a mineral including refractory auriferous sulphides This sub- product is normally vented into the atmosphere in current gold processing operations and is, therefore, wasted BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing an embodiment of the present invention, Figure 2 is a flow diagram showing another embodiment of the present invention, Figure 3 is a flow chart showing yet another embodiment of the present invention; Figure 4 is a graph of the degree of concentrate recovered from flotation versus grinding size of Examples 1-6; Figure 5 is a graph of the degree of Flotation tails versus grinding size Examples 1-6, Figure 6 is a graph of the recovery of the concentrate in percent by weight of the flotation against the grind size for Examples 1-6, Figure 7 is a graph of Gold recovered in the concentrate from flotation against milling size for Examples 1-6, Figure 8 is a flow chart for an embodiment of the present invention in relation to a pilot plant for Example 7, Figure 9 is a graph of the gold recovery in the concentrate from flotation against grinding size for Example 8, Figure 10 is a flowchart of an embodiment of the present invention including pre-tra Figure 11 is a flow diagram of the process of one embodiment of the present invention showing the recirculation of the flotation gas, Figure 12 is a section elevation showing aspects of an embodiment of a flotation apparatus of the present invention. Figure 13 is a section elevation of another embodiment of a flotation apparatus of the present invention. Figure 1 is a process flow diagram of a modality crushing circuit. of the present invention Figure 15 is a flow diagram of the process of one embodiment of the present invention including magnetic separation before flotation. Figure 16 is a process diagram of one embodiment of the present invention including a leaching Flotation and including the use of deoxygenated water Figure 17 is a process flow diagram of a method of the present invention having multiple flotation stages with grinding occurring between the flotation stages. Figure 18 is a graph with recovery representations of Sulfur sulfur against pH for Examples 9-28 Figure 19 is a graph that shows representations of gold recovery versus pH for Examples 9-28. Figure 20 is a graph that shows representations of incremental gold recovery and sulfur sulfur recovery in increment for Examples 9-28 Figure 21 is a graph that includes representations of gold recovery versus flotation time for Examples 29-35 Figure 22 is a graph of gold recovery against flotation time for Examples 29-35, Figure 23 is a graph including representations of gold recovery and oxidation-reduction potential versus flotation time for Example 36, Figure 2 is a graph that includes representations of gold recovery and oxidation-reduction potential versus flotation time for Example 37, Figure 25 is a graph that includes weight recovery versus flotation representations for Example 38 , Figure 26 is a graph that includes representations of gold recovery versus float time for Example 38, Figure 27 is a graph that includes sulfur sulfide recovery versus flotation representations for Example 38, and Figure 28 is a process flow diagram of one embodiment of the present invention using the gas generated in a step of pre-treatment with acid as a flotation gas DETAILED DESCRIPTION OF THE PREFERRED MODALITY The present invention provides a method for processing a mineral material including refractory auriferous sulphides to facilitate the recovery of gold from refractory gold sulfides. The method involves the preparation of a gold concentrate.

Flotation in a way that reduces the problems associated with conventional flotation Surprisingly it has been found that the problems associated with the concentration of refractory gold sulfides through conventional flotation can be significantly reduced through the use of a flotation gas, which It comprises a lower volume fraction of gas oxygen than the present ambient air. Preferably, the flotation gas must be substantially free of oxygen gas. When air is used as a flotation gas, the oxygen gas in the air seems to dangerously affect the Flotation capacity of refractory auriferous sulfides This may be due to surface oxidation of refractory auriferous sulfides caused by the presence of oxygen gas Surface oxidation could tend to depress refractory auriferous sulfides during flotation In addition, the hazardous effects of gas oxygen pu They can be further reduced by keeping the ore in an environment that is substantially free of oxygen gas during grinding, mixing, pumping and the other processing steps until a final flotation concentrate has been obtained. For example, when using multiple flotation steps , it is desirable to keep the ore in an environment that is substantially free of oxygen gas between the flotation steps By reducing the seemingly dangerous effects of oxygen gas, it is possible to recover a larger amount of the sulfide mineral species, including gold sulfides 7 refracting them, in the flotation concentrate The present invention, therefore, facilitates the recovery of gold from sulfide ore material that previously could have been discarded as waste, either with the gangue in a flotation tail or as Lower grade ore that was previously believed to be economical for gold recovery. The improved concentration, in accordance with the present invention, of sulfide minerals to the flotation concentrate provides a particular advantage with respect to the recovery of gold from refractory gold sulfides. This is because it has been found that refractory gold in a mineral Refractory sulfide is usually predominantly associated with refractory gold sulfides, mineralogical / morphological species of sulfide ore are very difficult to float effectively Therefore, the increase of gold recovery in the concentrate with the present invention usually it will be a percentage substantially larger than the percentage increase in the recovery of sulfide minerals. An important class of refractory auriferous sulfides are arsenical iron sulphides including arsenical pyrite, arsenical marcasite, and arsenical pyrrhotite. These gold sulfides are different in composition of pyrite, marcasite and pyrrhotite, respectively, since they include arsenic in the mineral network structure in a way that also allows the inclusion of gold in the mineral network structure in the form of a solid solution The inclusion of arsenic provides a certain amount of irregularity in the mineral network structure in relation to the painting of pure iron-sulfide minerals Irregularity provides space within the network of crystalline structure of the sulfide mineral to adapt to the presence of gold atoms in the network of crystal structure of sulfide ore in the form of a solid solution This irregularity also increases the susceptibility of the gold sulphides refractory to oxidation in the presence of air and to the Galvanic interaction, both are dangerous for flotation The arsenic content in these arsepical iron sulphides is usually in the range of about 0.01% by weight to about 10.0% by weight These arsenical iron sulfides can have a structure of crystalline network that varies from anhedral to euhedral Typically, iron sulfides to rsenical have a grain size and / or morphology that is fine ground amorphous, framboidal, microcpstalina, blastica or partially deoxidized Not all refractory auriferous sulphides, however, are arsenical iron sulphides, for example, sulfur species rich in arsenic, such as those based on orpiment (As2S3) and realgar (A6S), may include small amounts of iron in the crystal lattice structure of the ore that provides sufficient irregularity to allow inclusion within the crystal lattice structure of the gold ore in the form of a solid solution In addition, the arsenopyte (FeAsS) may contain gold in its crystal lattice structure of mineral in a solid solution, and may be a refractory auriferous sulphide Iron-refractory refractory sulfides rich in iron, containing arsenic (ie, arsenical iron sulfides) and refractory auriferous sulfides rich in arsenic, which contain iron are not classically recognized sulfur species since, generally speaking, they do not have the classic composition of pyrite, marcasite, pyrrhotite, orpimento or realgar, as should be the case. Most refractory auriferous sulfides fall into the category of chemical / structural variations of classical sulfur species that have not been systematically characterized based on their arsenic, iron and gold contents and their respective flotation capacities. However, few classically recognized pure sulfur minerals can include some amounts of gold in the network of crystal structure of the mineral and therefore, can also be refractory auriferous sulphides These include arsenopyte and its variations that appear to include some space within its crystal lattice mineral structures to accept significant amounts of gold in the form of a solid solution As an example of the concentration of gold in mineralogical species / morphological data difficult to float, a detailed mineralogical characterization is shown in Table 1 of sulfide species found in two samples of refractory sulfide ore A sample of ore is from the Lone Tree mine and the Another sample of ore is from the Twin Creeks mine both in Nevada, United States As shown in Table 1, the arsenical pyrite species represent a variety of mineralogical / morphological types. However, a common theme is that the gold content generally it tends to increase as the grain size and / or the morphological character becomes thinner. The coarse grain paint typically contains insignificant levels of gold, while the fine, amorphous, framboidal arsenical pint species all contain very high levels. Higher gold The arsemcal pinta species shown in Table 1 are arranged in an increasing thickness of grain size except for orpiment, marcasite and arsenopyte. These arsenical pints having finer grain size and / or morphological character are particularly benefited by the flotation of the present invention Also, as shown in Table 1, the marcasite arsepical and orpimento q It contains iron also include significant amounts of refractory gold Table 1 shows the refractory auriferous sulfide species of arsenical pyrite including coarse grain, blast, medium grain, fine / framboidal, amorphous, framboidal and framboidal morphologies As seen in the Table 1, these arsenical refractory gold sulfides (plastic, medium grain, fine / framboidal, amorphous, framboidal, and framboidal) have a much higher gold content than coarse-grained pure paint, which is substantially free of arsenic , what it has a network of crystalline structure of unbroken pint mineral that does not contain enough space to include gold atoms within the network of crystalline structure of the mineral Unlike coarse-grained pure paint, the refractory auriferous sulphides of arsenical iron sulfide all include sufficient amounts of arsenic to disrupt the network of mineral crystal structure of the species and allow gold atoms to be included within the network of crystalline structure of the mineral in a solid solution form TABLE 1 Not applicable 2 Average content of 5 fine grain samples of fine / amorphous material 3NI = S? N arsenic informatreported Second sample Percentage of Faith The finer grain size and the finer morphological character of a sulfide mineral makes the sulfide ore generally more susceptible to the damaging effects of the presence of oxygen in a flotatsystem to obtain a high gold recovery in the Therefore, it is extremely important that the flotatbe operated in a way that maximizes the flotatof those mineralogical morphologies that are very difficult to float. To illustrate this problem, Table 2 shows calculated losses of gold in flotattails for each equivalent loss of 1% sulfide ore to the tail for vain sulfide species shown in Table 1 As can be seen in Table 2, if a percentage of the sulfide material of the Lone Tree ore tends towards the tail, and that percentage is framboidal arsenical pyrite, then the corresponding loss of gold towards the tail is about 3% or a loss of gold that is proportlly more than three times the loss of refractory gold sulfide As can be seen for Twin Creeks the loss of framboidal arsenical paint results in the loss of gold which is proportlly more than ten times the loss of refractory gold sulfide. To illustrate Additlly, the experience of Lone Tree Twin Creeks and other minerals indicate gold recoveries only on the scale of 50 to 80% with recoveries of Conventl flotatof sulfide minerals on the scale of 75 to 95% For the Twin Creeks ore a flotatgold recovery of 87 to 90% in the concentrate is not achieved until the recovery of sulfur sulfur exceeds approximately 97% Promoting the flotatof refractory auriferous sulfides, the majority of the mineralogical / morphological sulphide species difficult to float, the present inventaddresses the need for extremely high sulfide mineral recoveries in the flotatconcentrate to obtain acceptable recoveries of gold TABLE 2 (1) Not applicable (2) Average content of 5 samples of fine grade fine / amorphous matepal grade One embodiment according to the present inventis shown in Figure 1. Referring to Figure 1, a feed of mineral material carrying gold 102 is provided for processing. Feed of mineral material 102 can be any gold bearing material comprising one. or more refractory gold sulfides, the refractory gold being predominantly associated, and from which the refractory gold is difficult to recover since it is not willing to direct cyanidat The sulfide species in the mineral material feed 102 may also include one or more non-refractory sulfide species such as pinna, marcasite and pyrrhotite, in additto the refractory auriferous sulfides, discussed above. The mineral material feed 102 is typically a complete mineral, but may be a residue from another processing or a previously discarded glue. matepal mineral 102 is subjected to crushing 104 for obtaining a particulate mineral material 106 having mineral particles of a size suitable for flotat The particulate mineral material 106 is preferably sized such that at least 80% by weight of the particles in the particulate mineral material are smaller than about 100 meshes, preferably smaller than about 150 meshes, and most preferably smaller than about 200 meshes The size at which 80% by weight of a material passes is usually referred to as a P80 size. Any operatcan be used. of pulverizatand / or grinding suitable for crushing 104 Spraying and / or wet grinding operat are generally preferred due to their relative ease and low cost compared to dry operat The grinding 104 is conducted in the presence of a mantle gas 108, which is obtained from a gas source 110. During, or before the grinding 104, the feed of mineral material 102 is mixed with the mantle gas 108, which contains oxygen gas, if not all, at a fraction of the volume of oxygen gas lower than that present in ambient air, to reduce the problems that can be caused by the presence of air during the grinding process. grinding 104 it is preferable to maintain a positive pressure of mantle gas 108 in any spraying and / or grinding apparatus to assist mixing of the feed of mineral material 102 with mantle gas 108, and displace any air that may be present with the feed of mineral material 102 After crushing 104, the particulate mineral material 106 is subjected to flotation 112 to remove the sulfide minerals, including auriferous sulfides s refractory, the gangue material without sulfur During flotation, a slurry of particulate mineral material 106 is aerated with a flotation gas 114 from a gas source 110 Any suitable flotation apparatus can be used for flotation 112, such as one or more of a flotation cell or a conventional flotation column. However, preferably the flotation apparatus it is such that a small positive pressure of the flotation gas 114 can be maintained in the apparatus to prevent the entry of air into the apparatus. The flotation gas 114 has oxygen gas, if any, at a fraction of volume reduced relative to the volume fraction of the oxygen gas in the ambient air, to reduce the problems associated with the use of air as a flotation gas. Although not required, the flotation gas 114 will normally be of a composition substantially equal to that of the mantle gas. In addition, normal reagents may be added during or before flotation 112 to aid flotation separation. Such reagents may include foaming agents, activators, harvesters, depressants, modifiers and dispersants. Flotation 112 can be conducted at room temperature. environment and a natural pH produced by the mineral material Operating conditions, such as pH and temperature However, they can be adjusted as desired to optimize the flotation separation for any particular mineral material. Out of the flotation 112 there is a flotation concentrate 116, which is recovered from the flotation foam and which is rich in water. sulphide minerals, and particularly in refractory auriferous sulphides and consequently also in gold in the refractory auriferous sulphides Also coming out of the flotation 112 is a flotation tail 118, which is rich in gangue materials without sulfur, and consequently contains low levels of refractory gold Flotation concentrate 116 can be further processed to recover gold through any suitable technique, if desired. Alternatively, flotation concentrate 116 can be sold as a valuable commodity to process others to recover gold.

As previously noted, the flotation gas 114 and mantle gas 108 each comprise oxygen gas, if any, at a volume fraction that is less than the volume fraction of oxygen gas in the ambient air. However, preferably the amount of oxygen gas in the flotation gas 114 and / or mantle gas 108 is less than about 15% by volume, and most preferably less than about 5% by volume. Very preferably, both the flotation gas 114 and the gas of mantle 108 are substantially free of oxygen gas. To help understand the present invention but not be limited by theory, it is believed that oxygen gas, if present in any appreciable amount, tends to oxidize the surface of refractory auriferous sulphides, which may have the effect of depressing the particle flotation of those sulfur species during flotation. 112 Reducing the amount of oxygen gas that comes into contact with the sulfur species is believed that any surface oxidation effect is reduced, resulting in improved flotation of the sulfide species, including refractory auriferous sulfides and a corresponding increase in the amount of sulfides and, therefore, Thus, it is preferred that the flotation gas 114 and the mantle gas 108 consist essentially of components that can not oxidize the surface of the sulfide mineral particles, and particularly, of gold, recovered in the flotation concentrate 116. those which include refractory auriferous sulfides. It is preferred that the flotation gas 114 and mantle gas 108 predominantly comprise one or more gases other than oxygen gas. Suitable gases include nitrogen, helium, argon and carbon dioxides. Preferably, one or more of these The gases should comprise more than about 95% by volume of the flotation gas 114 and the mantle gas 108, and most preferably more than about 98% by volume. Although it is preferable that the mantle gas 108 and the flotation gas 114 consist essentially of one or more of these gases Nitrogen gas is particularly preferred because of its relatively low cost Mantle gas 108 and / or fleet gas 114 may be introduced to the process apparatus in any appropriate manner. Such gases may be fed under positive pressure or may be induced into the apparatus by creating a suction that pulls the gas in. However, preferably the apparatus is designed to substantially prevent introduction of air to the crushing and flotation apparatus In one embodiment, the possible harmful effects of any surface oxidation of the sulfide mineral particles that may be present in the feed of mineral material can be counteracted by the addition of a sulfurizing agent, to at least partially replace the oxidized coating with a sulfide coating Any material capable of reacting to form the desired sulfide coating of the particle Mineral can be used Suitable sulphidating agents include alkali metal sulphides and disulphides, such as Na2S, NaHS, etc. These sulphiding agents can be added during grinding, conditioning just above the flotation or during any flotation stage. the present invention, more than about 80% by weight of sulfide minerals of the particulate mineral material 116 can be recovered in the flotation concentrate 116, and preferably more than 90% by weight of those sulfide minerals are recovered in the flotation concentrate 116 It should be noted that the fleet However, the flotation according to the present invention typically promotes the flotation of all the sulfide species present in the feed material. Thus, the compounds of the present invention are generally not selective as between the different sulfur species. Stronger sulfur species to float are properly concentrated in the flotation concentrate A major advantage of the process of the present invention is that, in addition to allowing a high recovery of gold sulfides refractories in the flotation concentrate 116, allows a high rejection of gangue material towards the flotation tail 118 Relative to the use of air as a flotation gas, the present invention allows the same recovery of gold in a weight concentrate to be obtained smaller This provides a significant economic advantage, since less gangue material is present in the concentrate, from which the gold must finally be separated to produce a purified gold product, if desired. The gas source 110 can be any source that provides an adequate flotation gas 114 and a mantle gas 108 A preferred gas source 110 is an installation wherein the nitrogen gas is separated from the air, the separated nitrogen gas being used as mantle gas 108 and the gas from flotation 114 Vanos processes are known to separate nitrogen from air, including cryogenic separation and membrane separation A particularly preferred gas source 110 is an oxygen plant, which is commonly found in existing facilities where refractory sulfide minerals are processed that carry gold. An oxygen plant is typically required, for example, when using a pressure oxidation operation or an oxidizing calcination operation in the processing of gold-bearing sulfide minerals In oxygen plant, oxygen is separated from air, such as through cryogenic separation or membrane separation, and separated oxygen gas is used in pressure oxidation or oxidation calcination operation A byproduct of said oxygen plant is a stream of effluent gas, which is rich in nitrogen gas and is suitable for use as mantle gas 108 and / or Flotation gas 114 This by-product stream has been previously vented to the atmosphere and, therefore, has been discarded. With the present invention, however, the by-product stream can be beneficially used to produce the flotation concentrate 116, in addition to use the oxygen gas product stream for pressure oxidation or oxidation calcination operation Another possibility for gas source 110 is a nitrogen plant dedicated to the production of a nitrogen rich gas to be used as mantle gas 108 and / or the flotation gas 114 A nitrogen plant differs from an oxygen plant in that the main product stream is a gas stream rich in nitrogen and the by-product stream is an oxygen-rich gas stream. The oxygen-rich gas stream from a nitrogen plant, however, is normally much lower in oxygen purity than an oxygen-rich stream from a plant Oxygen The nitrogen plant can be based on the operation of air towards a nitrogen-rich stream and an oxygen-rich stream through membrane separation, cryogenic separation or another form. Another possibility for the gas source 110 is a burner or Another combustion device for producing combustion exhaust gases that substantially lack oxygen. For example, the gas source 110 can be expelled from an electric power generator used to generate energy for a mine or mineral processing facility. combustion exhaust such as mantle gas 108 and / or flotation gas 114, it is preferred that the combusted fuel produce gases that are clean burned fuel such as natural gas, propane or other liquefied petroleum gas, or an alcohol such as methanol or ethanol Although less preferred, other fuels such as coal or fuel oils, including diesel fuel may be used. Yet another possibility for gas source 110 is a gas generated during the acid pre-treatment of a feed of mineral material 102 which includes carbonate minerals Carbon dioxide gas is generated from the decomposition of the min carbonate epoxies Carbon dioxide can be used as mantle gas 108 and / or flotation gas 114 Such modality is shown in Figure 10 As shown in Figure 10, the feed of mineral material 102 is subjected to the grinding 104 to form the particulate mineral material 106 The particulate mineral material 106 is then subjected to a pretreatment with acid 150, wherein the acid 152 is added to the particulate mineral material 106 to decompose the carbonate minerals present in the particulate mineral material 106 El particulate mineral material 106 remaining after pretreatment with acid is subjected to flotation 112, to form flotation concentrate 116 and flotation tail 118. During pre-treatment with acid 150, a gas that is rich in carbon dioxide and deficient in oxygen, is produced, which is used as mantle gas 108 and flotation gas 114 An alternative to acid pre-treatment of mineral material feed 102 is to use gases produced during acid pre-treatment of another carbonate-containing mineral material, such as a complete mineral, prior to pressure oxidation. Such a modality is shown in Figure 28. A further possibility for gas source 110 is to have liquid and compressed nitrogen, carbon dioxide or other gas supplied to the site In a preferred embodiment of the present invention, the flotation gas 114 is made, at least in part, recirculated gas from the flotation 112 This embodiment is shown in Figure 11, wherein a recirculating gas 156 of the flotation 112 is used as part of the flotation gas 114. Thus, the formation flotation gas 114 of the gas source 110 can be kept to a minimum This recirculation of gas from the flotation 112 provides the benefits of reducing the amount of formation gas that needs to be applied by the gas source 110 and reduces the oxygen deficient gas emission from the flotation 112 Reduction of the oxygen deficient gas emission of the Flotation 12 is particularly important when flotation 112 is conducted in an enclosed structure, where people are present, so that the ambient air in the structure is not seriously deficient in oxygen. In this regard, oxygen checks must be placed on any enclosed structure to ensure that sufficient oxygen is present for human needs Figure 12 shows aspects of an embodiment of the flotation apparatus 160 that can be used with the present invention to achieve recirculation of the flotation gas As shown in Figure 12, the flotation apparatus 160 has a sealed flotation tank 162, above which a motor 164 is mounted to rotate an arrow 166 extending downward towards the flotation tank 162 to activate an impeller 168 When the flotation apparatus 160 is operating , there is a superior vapor space 170 above a column of liquid 172 The gas from the upper vapor space 170 is withdrawn through a conduit 174 through a blower 176 which will be forced through a conduit 178 to be used as the flotation gas. The flotation gas from the conduit 178 is forced through of an annular conduit 180 near the impeller 168 so that the flotation gas can be properly distributed and dispersed through the liquid column 172 The formation flotation gas is provided through the conduit 182 to compensate for any loss of flotation gas in the system Figure 13 shows aspects of another embodiment of the flotation apparatus 160 for effecting recirculation of the flotation gas. In the embodiment shown in Figure 13, the flotation apparatus 160 is designed so that a blower is not used. 174 collects gases from the upper dome space 170 and cyclizes the gas to the annular duct 180 to be used as a flotation gas. The action of the impeller 168 causes a vacuum in the annular duct 180 creating sufficient suction to extract the floating gas through the duct 174 at a sufficiently high speed This type of flotation apparatus design 160, therefore, is self-inducing with respect to the introduction of flotation gas and does not require a blower or other gas compression device. Flotation without the use of a blower is important since recirculated flotation gas will normally contain a significant amount of water. corrosive vapors or gases or corrosive gases that could significantly corrode the inner surfaces of a blower Referring again to Figure 1, as previously noted, the flotation 112 can be performed at a natural pH However, it has been found to be preferred that flotation 112 is conducted at an acidic pH, and preferably at an acid pH that is less than about 6 A most preferred is a float pH scale of from about 3 to about 6 and most preferably is a pH scale of about 5 to about 6 pH control can be achieved through of the addition of an acid or a base as necessary to adjust the pH to the desired scale. For example sulfuric acid and / or any other acid can be added to the flotation 112 to reduce the pH and can be added lime, carbonate sodium, caustic soda or any other base during flotation 112 to increase the pH The acid to reduce the pH can come from any of the other ore processing steps, such as pressure oxidation or bio-oxidation, as discussed below In addition, acidification can be achieved by introducing sulfur dioxide to the flotation. 112 In its dissolved state in water, sulfur dioxide forms sulfurous acid Sulfur dioxide can be provided through the exhaust gas from a sulfur burner As previously observed, reactive spans can be used during flotation 112 However, it has been unexpectedly found that copper-based activators generally do not work as well as the lead-based activators used during flotation 112 Lead-based activators must contain lead in an oxidation state of +2 A preferred activator is lead nitrate Another preferred activator is lead acetate One benefit of using a lead-based activator, in relation to the use of a copper-based activator such as copper sulfate, is that higher recoveries are experienced in the flotation concentrate 116 for both sulfur minerals and gold Also, if the flotation tail is subjected to leaching with cyanide, as discussed below, the use of a lead-based activator provides the additional advantage of reducing cyanide consumption during the leaching operation relative to a copper-based activator. An additional advantage is that the consumption of cyanide for the final cyanide leaching of the gold contained in the flotation concentrate 116, such as after oxidation by pressure, the use of a lead-based activator will be lower compared to the use of a copper-based activator Another reagent that has been found to be particularly useful in flotation 112 is a xanthate collector. The appropriate xanthate collector may be provided through the addition to the flotation 112 of a xanthate salt such as potassium amyl xanthate or isopropyl xanthate. Sodium Improved performance through the use of a xanthate hardening reagent is significantly greater than normally expected, especially when compared to the operation of other widely used hardening reagents When the feed of mineral material 102 contains a significant amount of organic carbon , the organic carbon can significantly and dangerously intervene with the recovery of gold and sulfide minerals in the flotation concentrate 116 To reduce the harmful effects of organic carbon when present in the feed of mineral material 102 it has been found to be advantageous to add a floating oil 112 Axis These include an aromatic oil, such as collection of molybdenum, commonly referred to as MCO, or a non-aromatic oil such as diesel No 2 As discussed above, grinding 104 is conducted in the presence of mantle gas 108 Referring now to Figure 14, a mode of a crushing circuit As shown in Figure 14, the ore feed 112 is fed to a first crushing unit 186, such as a buckling mill In the first crushing unit 186, the particles of mineral material in the feed of mineral material 102 are reduced in size The outlet of the first crushing unit 186 passes through a screen sieve 188 in a sealed discharge box 190 The mantle gas 108 is fed to the discharge case 190, so that the mantle gas will flow through the first crushing unit 186 in a counterflow with the feed of mineral material 102, to ensure the removal of air from the food mineral material 102 The material leaving the discharge box goes to a tank 192 to supply a cyclone separator 194 through a pump 196 The cyclone separator 194 classifies the mineral material by the particle size to an overflow 198 of smaller sized particles and a subflow 200 of larger sized particles The subflow 200 is then fed into the sealed feed box 201 of a second grinding unit 202, such as a ball mill, to further reduce the size of the particles of the mineral material in the subflow 200 The discharge of the second grinding unit 202 passes through a screen sieve 204 in a sealed discharge box 206 The mantle gas 108 is fed both to the feed box 201 and to the discharge box 206. material exiting the discharge box 206 goes to a tank 208 where it is combined with the overflow 198 of the cyclone separator 194 The discharge of the tank 208 goes to a cyclone separator 210 through a pump 212 The cyclone separator 210 it separates particles by size towards an overflow 214 comprising particles of smaller size and a subflow 216 comprising larger sized particles The subflow 216 of the cyclone separator 210 is fed to the second milling unit 202 together with the subflow 200 from the cyclone separator 194 The overflow 214 of the cyclone separator 210 goes to the tank 218, wherein the particulate mineral material in the overflow 214 can be maintained for feed to flotation processing. It should be noted, as shown in Figure 14 all the process equipment is sealed, except for feeding to the unit. In addition, the mantle gas 108 is introduced at various points in the grinding system to ensure minimum air entering the system. As shown in Figure 14, the mantle gas 108 is specifically fed into the housing. discharge 190 of the first crushing unit 186 to the tanks 192, 208 and 218, towards the cyclone separators 194 and 210 and to the feed box 201 and the discharge box 206 of the second milling unit 202 In addition to maintaining the grinding environment in the absence of any significant amount of air it is important for the operation of the subsequent operations of flotation that the effects of galvanic interaction are reduced as much as possible during the crushing of the feed of mineral material 102 Said galvanic interactions are due to different electrochemical activities on different surfaces of material The combination of a cathodic surface (ie pyrite pyrrhotite arsenical etc.) and an anodic surface (ie iron from the crushing media or steel walls of mill linings) results in the creation of a galvanic cell during crushing processing. Galvanic cells also exist between the different sulfide minerals that They can be present and n the feeding of mineral material with the sulfide material with the highest resting potential acting as the cathode and the sulfide mineral with the lowest resting potential acting as the anode For example the galvanic interaction between the ground iron and vain forms of refractory auriferous sulphides and especially arsenical iron sulfides can be represented by the following reactions iron surface grinding (anode) Fe = Fe 2 + 2e Ec 1 surface of refractory auriferous sulfide (cathode)% 02 + H20 + 2e = 20H "Ec 2 For example, during grinding, galvanic cells are created each time a surface of refractory gold sulfide is brought into contact with grinding media, mill liners, abrasive trap iron or any other metal sulfide at a resting potential lower or higher These galvanic interactions create hydroxide coatings on the surfaces of the refractory auriferous sulfides, reducing their flotation capacity. In accordance with the present invention, said damaging galvanic interactions can be prevented by reducing the amount of oxygen present during the grinding to However, it has been found that in addition to reducing the amount of oxygen present during the grinding operation, improved flotation results can be obtained by further limiting the iron contamination of the mineral material being processed. combination of reducing the amount of iron introduced into the mineral material and the use of mantle gas 108 provides an increase in the recovery of gold in the flotation concentrate that could be unexpected based on the contributions of each one only One way to reduce the amount of iron available for interactions galvanic during crushing processing is using grinding media made of a steel hardened with chromium or nickel or a corrosion resistant steel such as stainless steel Although ceramic grinding media can be used, the ceramic grinding media is typically not of sufficient density for effective grinding Another way to reduce the harmful galvanic effects of iron is to provide all crushing equipment such as sprays and mills with non-metallic liners and preferably with rubber liners. An additional and preferred method for reducing the harmful galvanic interactions caused by iron during the Flotation is to perform a magnetic separation step after grinding and before flotation Referring to Figure 15, a modality including a magnetic separation step after grinding is shown As shown in Figure 15 the material feed mineral 102 is first subjected to the grinding 104 followed by magnetic separation 230 to remove the particles of magnetic material 232 from the mineral material 106 As an alternative to the modalities discussed above, it should be noted that many of the advantages of the present invention can be obtained even without the use of mantle gas 108. In this regard, most conventional crushing circuits use equipment that freely allows that the air enters the system With the present invention however when it is not practical or economical to use a gas of The improved operation can still be obtained by sealing all the equipment involved with the grinding processing so that substantially the only oxygen entering the grinding processing enters with the feed of mineral material 102 to be processed. In this respect, said system crushing can be substantially as described with respect to Figure 14, with all the process equipment sealed to prevent air from entering and without feeding any mantle gas 108 into the process equipment Oxygen already present in the feed of mineral material 102 can be consumed through the oxidation of the surfaces of sulphide mineral particles exposed during grinding Once all the original oxygen has been consumed, however, the continuous harmful effects of oxygen could be substantially eliminated Although this mode of operation is not as preferable as using mantle gas 1 08, it is preferred that a system be open to the introduction of air, as is common practice To further reduce the amount of oxygen introduced into the system to reduce the damaging effects of surface oxidation of sulfide minerals and galvanic interactions, it is preferred that the processing water used to grind the mineral material for crushing processing and / or flotation processing has been deoxygenated Deoxygenation of process water can significantly improve recovery in mineral concentrate of sulfur and gold during flotation processing Deoxygenation can be performed in any convenient manner, such as by bubbling an inert separation gas, such as nitrogen or carbon dioxide, through the process water to remove oxygen from the process water or adding an oxygen scavenger to the water to bind the oxygen It has been found that a flotation tank works well for deoxygenation by introducing nitrogen or carbon dioxide into the vessel to perform the oxygen separation function. Alternatively, the inert separation gas can be spraying in a tank containing the process water Preferably, the process water must be deoxygenated at a level of dissolved oxygen that is less than about 2 0, preferably less than about 10, and most preferably less than 0 5 parts per million oxygen by weight Also, with the present invention, it is possible to use recirculated water as the Process water When using recirculated water, however, it is important that an activator be used during flotation processing. This is because any cyanide in the recirculating water that is available for reaction with the sulfur sulfur or sulfide minerals will tend to to depress the flotation of the sulfide minerals and, consequently, reduce the recovery of the gold in the concentrate. However, the activators counteract the effect of depression that the cyanide has on the flotation. Also, the recirculating water can be treated with a material such as ammonium bisulfite, sulfur dioxide, a peroxide, Caro acid or any other known cyanide destruction technology used to destroy the cyanide before using the recirculating water for the flotation As noted with respect to the Figure 1, a preferred gas source 110 for mantle gas 108 and flotation gas 114 is an oxygen plant. Figure 2 shows an embodiment of the present invention wherein both the oxygen gas product stream and the current Nitrogen gas byproduct of an oxygen plant are both used to process the gold bearing sulfide mineral material. Referring to Figure 2, the particulate mineral material 110 is subjected to flotation 112 to produce the flotation concentrate. and the flotation tail 118, as previously described. Flotation gas 114 is a by-product stream rich in nitrogen gas from e an oxygen plant 130, wherein the air 132 is separated into an oxygen-rich gas stream (treatment gas 128) and a nitrogen-rich gas stream (flotation gas 114) The flotation concentrate 116, which is rich in refractory auriferous sulfides , is subjected to oxidation by pressure 124 to decompose the sulfide minerals, producing an oxidized material 126 from which the gold can be recovered by dissolution using any suitable gold lixiviant, such as a cyanide. Oxidation by pressure 124 involves treating a grout of the flotation concentrate 116 in an autoclave at a temperature greater than about 150 ° C and at a high pressure in the presence of an overpressure of a treatment gas 128 which is rich in oxygen It should be noted that other steps of oxidant treatment can be used instead of oxidation by pressure 124 For example, an oxidizing calcination or bio-oxidation can be used to produce the oxidized material 126 using the treatment gas 128. A further embodiment according to the present invention is shown in Figure 3 which uses the product and by-product gas streams for an oxygen plant for processing a sulfide mineral material carrying gold provided in two separate feed streams Referring to Figure 3 a first feed of particulate mineral material 138 is subjected to flotation 112 to produce the flotation concentrate 116 and the flotation tail 118 as previously described The flotation gas 114 is a stream of nitrogen-rich gas from the oxygen plant 130. A second feed of particulate mineral material 140 is combined with the flotation concentrate 1166 in a mixing step 142. The combined com pound 144 in the shape of a slurry is subjected to pressure oxidation 124 to produce the oxidized material 126 from which the gold can be recovered. An advantage of the embodiment shown in Figure 3 is that it allows the processing of multiple minerals having different For example, the first mineral material feed 138 may comprise a lower grade refractory sulfide mineral than the second mineral material feed, which may comprise a higher grade refractory sulfide mineral. The higher grade mineral may be suitable for pressure oxidation in a complete mineral form, while the lower grade ore must be graduated to a concentrated form to be suitable for pressure oxidation Alternatively, the second feed of mineral material may comprise a refractory sulfide mineral, which has a significant amount of carbonate material that may require the addition of acid prior to pressure oxidation 124, and, therefore, may cause high operating costs compared to minerals with low carbonate levels that detrimentally interfere with the proper operation of pressure oxidation 124 A high sulfur sulfide content in flotation concentrate 116, however, tends to produce an additional acid during the pressure oxidation to at least partially divert the acid consumption effect of the carbonate material in the second feed of mineral material Most of the carbonate material that was present in the first feed of mineral material, if any, could ordinarily be removed during flotation 112 With the present invention, the may ore gold reports to the flotation concentrate gold in the concentrate, which typically it is substantially refractory gold associated with one or more refractory auriferous sulphides, then it can be released for recovery operations through oxidizing processing, such as pressure oxidation, oxidizing calcination or bio-oxidation. However, many feeds of mineral material contain a significant amount of gold that is not associated with a sulfide mineral For example, it is not common for a refractory sulfide mineral bearing gold to also contain some gold in association with oxidized minerals or silica Up to 50%, and in some cases still more, gold in a refractory sulfide mineral can be associated with minerals other than sulphide minerals. Also, refractory sulfide minerals that have been stored in large quantities for a significant amount of time and therefore are exposed to air for a period of time. significant, can contain even greater amounts of gold that are no longer maintained by refractory auriferous sulfides. This is that a significant amount of a refractory gold sulfide can be oxidized so that a significant amount of gold is no longer associated with refractory gold sulfide. , a refractory sulphide mineral stored for several months can be oxidized to a degree where 20% to 30% or more of the gold is no longer associated with the refractory gold sulfide. The present invention has been found to work very well for the treatment of feeds of mineral material that have both refractory gold associated with sulfide minerals and non-refractory gold that is not associated with sulfide minerals Gold that is not associated with sulfide minerals, and especially gold associated with oxidized minerals, can be recovered after flotation processing by leaching the flotation tail Although any compatible leaching operation can be used, a preferred leaching operation is cyanide leaching. One embodiment of the present invention involving the leaching of the flotation glue is shown in Figure 16. Referring to Figure 16, a feed of mineral material 102 is provided having both refractory gold, refractory gold sulphide, and non-refractory gold that is not associated with sulfide minerals, and, therefore, will not float together with the sulfide minerals. The mineral matepal feed 102 is subjected to grinding 104 to prepare the particulate mineral material 106, which is then subjected to flotation 112 After flotation 112, flotation tail 114 is subjected to oxygenation 240 followed by a leaching 242 of flotation glue 114. Preferred for leaching 242 is a leaching of pulp carbon cyanide, although leaching can be used instead of carbon cyanide in leaching Leaving from leaching 242 is loaded carbon 244 that is loaded with gold Also leaving leaching 242 is a leaching tail 246 that has no gold Charged carbon 244 can be processed in a known manner to recover the gold Referring continuously to Figure 16, grinding 104 and flotation 112 are performed in the presence of mantle gas 108 and flotation gas 114, respectively supplied from gas source 110. Also shown in Figure 16, water process 248 is subjected to deoxygenation before using process water 248 in the process. Therefore, according to the embodiment shown in Figure 16, process water 248 is first deoxygenated in deoxygenation step 250, and, after flotation 112, water with flotation tail 118 is then oxygenated in oxygenation step 240 before leaching 246 Oxygenation 240 can be achieved in a suitable manner to increase the amount of oxygen dissolved in the slurry liquid of the flotation tail 118 Typically, the flotation tail slurry 118 is subjected to aspersion or bubbling with air or an oxygen rich gas. Oxidation 240 can be conducted using air or a gas rich in oxygen, since it could be suitable for the oxidation processing by pressure, as previously discussed. Although the modality described with respect to Figure 16 includes deoxygenation of the process water, said deoxygenation is required. Deoxygenated process water, however, tends to improve gold recovery from the process. The ability to successfully leach leach tail 118, as shown in Figure 16, results from the efficient separation of sulfide minerals from the concentrate during the floating 112 If a significant amount of the sulfide mineral were to be reported to the flotation tail 118, then the operation of the leaching 242 can be significantly impaired due to the sulfur sulfide of the sulfide ore that the cyanide can consume during a leaching of cyanide. the refractory gold in the flotation tail associated with the refractory auriferous sulfides could not be leachable With the present invention, however, the cyanide consumption is reduced during the leaching 242 since the efficient reporting of sulfide minerals towards the flotation concentrate 116 and the relative absence of the sulfide minerals in the flotation tail 118 Another significant advantage of the process of the present invention is that it allows the intermediate regrind of the particulate mineral material between the flotation stages (to improve the recovery of gold in the concentrated) Blistering intermediate can significantly improve r recovery of refractory gold in refractory sulphide gold mineral fragments trapped in medium particles In comparison, with conventional flotation using air as the flotation gas, said intermediate milling could also reduce the flotation capacity of refractory gold sulfides due to the harmful effects of oxygen Figure 17 shows a process diagram for an embodiment according to the present invention involving the regrind of the particulate mineral material intermediate between the flotation stages. As shown in Figure 17, a mineral material feed 112 is subjected to a first crushing step 254 to produce a particulate mineral material 106, which is then subjected to a first flotation stage 256. The first float stage 256 includes a more rigid float 258 in a float. stiffer sweeper 260 In the stiffer float 258, the particulate mineral material 106 is separated through flotation to a stiffer concentrate 262, which is part of a final concentrate 264 and a stiffer tail 266, which is fed to the stiffer sweeper float 260 The stiffer sweeper float produces a stiffer sweeper concentrate 268 and a stiffer sweeper tail 270 The stiffer tail 266, the stiffer sweeper concentrate 268 and the stiffer sweeper tail 270 they usually include a substantial amount of average particles. These average particles include refractory gold sulfides. two with the gangue material, such as silicas In addition, the stiffer sweeper tail 270 will typically include a sufficient amount of very fine particles To remove the very fine particles and allow the recovery of the sulfide mineral fragments from the average particles, the stiffer sweeper tail 270 is subjected to a size separation 274, as can be achieved using a sieve or a classification cyclone. A first fraction 276, comprising the finer particles of smaller size becomes part of a final tail 278 For example a 500 mesh screen can be used in the size separation 274 with all the particles passing through the screen and being sent to the final tail 278 as fine particles. A second fraction 280 of the size separation 274, which comprises particles of larger size, is sent to a second grinding step 284 together with the stiffer sweeping concentrate 268. In the second grinding step 284, the particles are crushed to a smaller size to break the middle particles and release the sulfide mineral fragments, including refractory gold sulfide fragments The 286 regrooved mineral material is to send it to a second flotation stage 290 for the concentration of the sulfide mineral fragments released from the average particles. The second flotation stage 290 includes a cleansing float 292 and a cleansing scavenger float 294. In the cleansing float 292, a cleansing concentrate 296 is produced, which is sent to form part of the final concentrate 264. The cleansing float 292 also produces a cleaning glue 298, which is sent to the cleaning sweeping float 294 In the cleaning sweeping float 294, a cleaning sweeping concentrate 300 was prepared, which is recirculated to the second grinding step 284 for further processing The sweeping flotation Cleaner 294 also produces a sweeping glue cleaner 302 that is sent to form part of the final glue 278. Also shown in FIG. 17 is the gas source 110 which supplies the mantle gas 108 to the first grinding step 254 the second grinding step 284 and the size separation 274 The gas source 110 also provides the flotation gas 114 to the stiffer float 258 the stiffer sweeping float 260 the flotation of the cleaner 292 and the sweeping float cleaner 294 The use of mantle gas 108 and flotation gas 114 substantially avoids the problems that could occur if the grinding and / or flotation operations were conducted in the presence of air. In addition, since the harmful effects of air are reduced, it is possible to have the second Intermediate crushing step 284 between the first flotation stage 256 and the second flotation stage 290 without destroying the flotation capacity of the sulphide minerals in the mineralized material 286 The second crushing step 284 significantly improves the operation of the flotation circuit This is why it does not it will be necessary to crush all the feed of mineral material 102 to a very fine size that may be required to release refractory gold sulfides from the middle particles in the first crushing step 254 Having a coarser grinding for the particulate mineral matepal 106 is significantly less expensive than crushing the entire feed of mineral material 102 to a size small enough to release the fragments of refractory gold sulfide ore of the average size Also a coarser grinding to produce the mineral material in particle 106 simplifies the operation of the first flotation stage Average particles of the first flotation stage 256 are then crushed additionally in the second grinding step 284 for releasing the blocked refractory auriferous sulfide mineral fragments for recovery in the second flotation stage 290. The present invention is further described through the following examples, which are intended to be illustrative only and they are not limited to the scope of the present invention EXAMPLES Examples? -6 Examples 1-6 demonstrate the use of nitrogen gas as a flotation gas during the flotation of a sulfide ore bearing gold to produce a sulfide-rich concentrate, which can be further processed to recover refractory gold in refractory gold sulfides, if desired For each of Examples 1-6, a sample of Santa Fe Pacific Gold Corporation's Lone Tree Mine ore was provided in Nevada. The ore samples are from a low grade refractory sulfide mineral that may be inconvenient for oxidation by economic pressure in a form of complete mineral. A representative test of a mineral sample is shown in Table 3.

TABLE 3 For each example, the ore sample was milled to the desired size. A first portion of the ore sample was floated in a laboratory-scale flotation cell using air as the flotation gas. A second portion of the ore sample was subjected to flotation under the same conditions, except that a flotation gas was used which consisted essentially of nitrogen gas. During each flotation test, a flotation foam was collected from the upper part of the flotation cell to recover a flotation concentrate, which is rich in sulfur minerals, influencing refractory auriferous sulphides, and which, therefore, is also rich in gold. The flotation tail is that material that was not collected in the foam. For each flotation test the flotation conditions are substantially as follows A natural pH and the addition of potassium amyl xanthate and mercaptobenzothiazole as harvesters, copper sulphate e for the activation of sulfides and MIBC as a foam Flotation times vary from 20 to 30 minutes The results of Examples 1-6 are shown tabularly in Table 4 and graphically in Figures 4-7 and reveal a significant increase in the amount of gold recovered in the concentrate when nitrogen gas was used as the flotation gas, especially at smaller grinding sizes TABLE 4 milliliters of gold per kilogram of glue (4) percentage by weight of the mineral sample feed reporting to the concentrate (5) percentage of gold in the mineral sample feed reporting to the concentrate Figure 4 graphically shows the degree of concentrate of flotation (measured as milliliters of gold per kilogram of concentrated material) as a function of ground size As seen in Figure 4, no identifiable effect on the degree of concentrate is evident from the use of nitrogen gas in relation to the use of air in flotation Figure 5, however, shows that the flotation tail at smaller milling sizes contains a significantly lower gold value when nitrogen gas is used as a flotation gas than when air is used. Therefore, when nitrogen gas is used, more of the refractory auriferous sulfides are recovered in the concentrate, evidently without any harmful effect on the degree of the recovered concentrate. Figure 6 shows that the amount of material recovered in the concentrate can be significantly larger when gas is used. nitrogen as a flotation gas that when air is used, especially in smaller grinding sizes o Figure 7 shows that the recovery of gold in the concentrate can be increased to almost 15% at a grinding of P80 of 270 mesh, when nitrogen gas is used as the flotation gas as opposed to air, again without any effect harmful to the degree of the recovered concentrate It should be noted that a P80 grind of 100 mesh does not exist any significant difference in the operation of the flotation when nitrogen gas opposite the air is used as the flotation gas. Therefore, it is surprising and unexpected that the Operation using nitrogen gas can be improved notably in relation to air at smaller grinding sizes Typically, it is expected that the flotation operation should be improved with a smaller grinding size due to a more complete release of sulfide minerals from the gangue material without sulfur However, as see in Figure 7, recovery of concentrate when air is used as the flotation gas is flat, at most. When nitrogen gas is used, however, the recovery of gold generally increases with the reduced grinding size due to the release of increased sulfide ore particles, including refractory auriferous sulfides, as is normally expected A form to explain the unexpectedly poor flotation performance when air is used, to aid understanding of the invention but is not bound by theory, is that some harmful chemical process can occur when air is used as a floating gas n, with the harmful chemical process counteracting the normally beneficial effects of a smaller grinding size It is observed that when air is used as the flotation gas, the pH of the grout in the flotation cell drops rapidly for a few minutes, sometimes falling as much as 0 5-2 pH units. Therefore, it is evident that oxygen in the air may be oxidizing the surface of sulfide mineral particles, and particularly those refractory gold sulfides, producing sulfuric acid and reducing the pH of the sulfuric acid. Grout Said surface oxidation of mineral particles of sulfur may be that you respond less to flotation As grinding becomes smaller, the surface area available for the oxidation of sulfides is significantly increased and, therefore, any beneficial effect of more complete release of sulfides due to smaller grinding size it is biased by increased surface oxidation, further depressing the flotation of refractory gold sulfides. However, nitrogen gas can not oxidize the surface of sulfide minerals and, therefore, allows for better flotation of the sulfide ore particles, resulting in a higher recovery of the sulfide minerals to the smaller grinding sizes, as is normally expected EXAMPLE 7 This example further demonstrates the beneficial use of nitrogen gas in the flotation of refractory sulfide minerals bearing gold, and the use of a cleaner and stiffer flotation arrangement to improve concentrate recovery. A pilot flotation plant is operated using a low grade refractory sulfide mineral from the Lone Tree Mine, as previously described in Examples 1-6 The flow from the pilot plant is shown in Figure 8 Referring to Figure 8, the ore sample 166 is subjected to crushing 168 in a ball mill to a P80 size of 270 mesh. The ground ore, in a slurry 170, is introduced to a more rigid flotation step 172 more rigid flotation passage 172, an initial flotation separation is made with a stiffer concentrate 174 being collected with the flotation foam and a stiffer tail 176 being sent to a sweeping flotation passage 178, the material collected in the foam of the floatation foam from the sweeping float step 178 is formed into new pulp and is introduced, as a slurry 179 to a cleaning float step 180, where a final flotation separation is made to produce a cleaning concentrate 182 of the foam and a cleaning glue 184 The cleaning glue 184 is combined with a sweeping glue 186, from the sweeping float passage 178, to produce the final glue 188 The stiffer concentrate 174 and cleaning concentrate 182 combine to form a final concentrate 190. In this example, the most rigid flotation step 172 is achieved in an individual double compartment flotation cell., Sweeper Flotation Step 178 is achieved in a series of three double compartment flotation cells, and Cleaner Flotation Step 180 is achieved in a series of three double compartment flotation cells As shown in Figure 8 , the nitrogen gas 192 is supplied from the gas tank 194 and is fed to each of the grinding step 168, the stiffer float passage 172, the sweeper flotation step 178 and the flotation step of cleaner 180 The nitrogen gas 192 is used as a flotation gas in each of the flotation steps and is used as a mantle gas to prevent air from oxidizing the particles of the ore during the crushing 168 nitrogen is also used to form a blanket throughout the process equipment, not shown, such as pumps and mixing tank. The refractory auriferous sulfides in the ore sample 166, therefore, are maintained in a substantially air-free environment. Throughout the pilot plant, until the refractory auriferous sulphides have been recovered in a desired concentrated product The results of the pilot plant are shown in table 5, which shows that the final concentrate 190 of the pilot plant is of a quality greater than the concentrates shown in Examples 1-6 The addition of the sweeper flotation step 178 and the flotation step of cleaner 180 in the pilot plant significantly improves the degree of concentrate finally recovered without any appreciable loss of gold recovery TABLE 5 LONE TREE PILOT PLANT Example Gold Grade Recovery Grade Mesh that grinds concentrate cola ml of from report to P80 -, '< ') final ml of gold / kg (31 concentrated concentrate gold / kg final percent percentage in gold weight' 'recovered'5' 270 17 8125 0 2968 94 864 rp- 80 percent by weight of material that passes the indicated size milliliters of gold per kilogram of respective concentrate milliliters of gold per kilogram of tail end < 4 > percentage by weight of the mineral sample feed reporting to the respective concentrate < 5) percentage of gold in the concentrate relative to the feed for the respective flotation step EXAMPLE 8 Laboratory tests were performed on samples of a refractory sulfide bearing low grade Gold from Santa Fe Pacific Gold Corporation's Twm Creeks in Nevada A representative analysis of a mineral sample is shown in Table 6 For each test, a sample was milled at Appropriate size and a proportion of each sample was then floated using air as the flotation gas and another portion was floated using a hydrogen as the flotation gas Substantially the same flotation conditions were used as those described for Examples 1-6 TABLE 6 The results of Example 8 are shown graphically in Figure 9, which shows a graph of gold recovery in the concentrate as a function of ground size. As seen in Figure 9, the use of nitrogen gas generally results in a recovery significantly higher gold in the concentrate compared to the use of air as a flotation gas Examples 9-28 These examples demonstrate the importance of flotation pH and the choice of activators to be used during flotation with the present invention. A series of laboratory flotation tests were performed using samples of refractory sulfide ore bearing low grade gold from Lone Tree. of the flotation each sample is ground to a P80 size of approximately 60 microns A test series was performed using a nitrogen atmosphere in the mill and nitrogen flotation gas with a variable flotation pH using lead nitrate as the activator. A second test was performed using air as the atmosphere of grinding and air as the flotation gas at variable pH values of flotation and using lead nitrate as the activator A third series of tests was performed using nitrogen as the milling environment and nitrogen as the flotation gas with variable pH values of flotation and using copper sulfate as the activator The pH was adjusted either through the addition of sulfuric acid or calcium hydroxide, as required Also, other flotation reagents were used Normal in each test The conditions for milling and flotation for each example are shown in Table 7 and the specific reagents used with each example are shown in Table 8 The results of the flotation are shown tabularly in Table 9 and graphically in the Figures 18-20 Figure 18 has sulfur sulfur recovery charts in the flotation concentrate versus the flotation pH for each of the three test senes Figure 19 has gold recovery charts in the flotation concentrate against the Flotation pH for each of the three test senes As seen in tables 7-9 and Figures 18 and 19, grinding and flotation using nitrogen gas provides significantly improved performance with ratio to air for all pH values, but for higher pH values In addition, the gold recoveries in the concentrate are better at acidic pH values, and particularly at pH values below about 6 In addition, very surprisingly , lead nitrate as activator consistently shows a significantly higher gold recovery in the concentrate than the more normal copper sulfate activator. Figure 20 includes a graph of the difference in percentage of gold recoveries in the concentrate using nitrogen versus air for vain pH values of flotation and a graph of the difference in the percentage of recovery of sulfur sulfur in the concentrate using nitrogen against air for vain pH values of flotation A dramatic effect of pH is revealed in Figure 20 at values of Lower pH For example, at a pH of 6, the gold recovery in the concentrate increases by more than 15 points percent for nitrogen versus air with less than a 5 percent increase in points in sulfur sulfur recovery These results also indicate that refractory gold is mainly associated with the types of sulfide ore that are particularly difficult to recover in the concentrate using conventional flotation with air as a flotation gas Those types of hard-to-float sulphide ore float extremely well however, with the use of nitrogen, especially when an activator containing lead is used an advantageously acidic pH These results, especially at a pH below 6, are particularly surprising. TABLE 7 TABLE 8 Ethyl glycol potassium amyl xanthate TABLE 9 Examples 29-35 This example demonstrates the importance of the selection of a collecting reagent to perform the flotation of the present invention. Laboratory flotation tests were performed on samples. of refractory sulfide ore bearing low-grade Twin Creeks gold at a pH of about 5 about 6 using collector reagent spans in equivalent amounts of cost A list of the different collector reagents, companies supplying the reagents and the amount of Each harvested reagent used is shown in Table 10 Nitrogen gas was used in the milling and as the flotation gas The particles were sized to a P80 size of approximately 46 microns and the flotation was conducted in a slurry with 30% solids. of ore are from a refractory sulfide ore bearing low grade gold having approximately 2 25 milliliters per kilogram of gold and approximately 5 58 percent by weight of sulfur sulfur. Other reagents used during the flotation tests are shown in table 11. The results of the flotation tests are shown in the Figures 21 and 22, which plot the percentage of recovery of gold in the concentrate against the flotation time for the reactive collector spaces. As shown in Figures 21 and 22, the potassium amyl xanthate worked much better than the other collectors with the flotation of the present invention TABLE 10 (2) Octyl ethyl sulphide, dialkyl dithiophosphate, polyglycol alkyl alkyl ether, sodium alkyl mercaptobenzothiazole sodium dnsoamyl dithiophosphate Dusobutyl sodium dithiophosphate t-dodecyl mercaptan Xanthogen formate TABLE 11 Example 36 This example demonstrates the importance of the milling medium in the operation of the flotation of the present invention. The laboratory flotation was conducted in samples of refractory sulfide ore bearing low grade gold from Lone Tree using nitrogen during milling and during the milling process. Flotation as Flotation Gas All samples were ground to a P80 size of approximately 44 microns One sample was crushed using stainless steel rods, while the other sample was milled using conventional medium steel balls Flotation results are shown graphically in Figure 23, which includes a graph of the percentage of recovery of gold against the flotation time for each sample and a plot of the oxidation reduction potential against the flotation time for each sample As shown in Figure 23, the sample milled with stainless steel bars exhibits substantially higher gold recovery at all times of flotation Importantly, a high gold recovery is achieved in a much shorter flotation time for the milled sample with the stainless steel bars than for the milled sample with the medium steel balls This distinction is important since it indicates that flotation times can be reduced with the use of stainless steel or other means of crushing such as steel hardened with an alloy with a high chromium content, which could introduce less reactive iron to the flotation system Example 37 This example demonstrates a surprising effect for performing a magnetic separation on a mineral sample before flotation according to the present invention. Samples of the refractory sulfide ore carrying Lone Tree subgrade gold were subjected to laboratory flotation. crushed to a P80 size of approximately 270 meshes After grinding, one sample was subjected to magnetic separation to remove the magnetic iron particles before flotation, while the other sample was not submitted The results are shown graphically in Figure 24, which includes a graph of the percentage of gold recovery in the flotation concentrate versus the flotation time and a potential oxidation-reduction graph in the flotation slurry against the Flotation time As seen in Figure 24, gold recovery is significantly greater for the sample subjected to magnetic separation. The effect is particularly pronounced at shorter float times, but even after 30 minutes of flotation, the sample that was submitted to magnetic separation exhibits a good gold recovery that is approximately a percentage of 10 points higher than the sample that was not subjected to separation Example 38 This example demonstrates the important effect with the present invention of using deoxygenated process water. Samples of a refractory sulfide ore bearing low grade gold from Twin Creeks were subjected to laboratory flotation. The samples contain approximately 2 25 milliliters per kilogram of gold. and about 58 percent by weight of sulfur sulfur. Spraying was performed under a nitrogen atmosphere for each sample and flotation was performed using nitrogen as the flotation gas. sized to a P80 size of about 46 microns A sample was formed in slurry with regular water for flotation The other sample was formed in slurry with tap water that was deoxygenated and bubbling nitrogen gas through the water for a sufficient time to remove most of the oxygen previously dissolved in the water The results of the flotation for each sample are shown in Figures 25-27 Figure 25 includes a graph of the recovery in weight in the concentrate against the flotation time for each sample, and shows that flotation with the deoxygenated water that has a higher weight recovery in the flotation concentrate Figure 26 includes a graph of gold recovery in the concentrate versus the flotation time for each sample, and illustrates that at the most flotation times long, gold recovery is higher using deoxygenated water Figure 27 includes a recovery graph Sulfur sulphide concentration in the concentrate against flotation time, which illustrates that, at longer flotation times, sulfur sulfur recovery in the concentrate is higher using deoxygenated water Recoveries of gold and sulfur sulfur increased indicate a significantly higher recovery of refractory auriferous sulfides in the concentrate Examples 39-57 These examples demonstrate the benefit of a leaching of glue with the present invention Samples of a refractory sulfide ore that carries Lone Tree subgrade gold were subjected to laboratory flotation Each sample was ground to a P80 size of approximately 270 meshes in an atmosphere The flotation was conducted with a nitrogen flotation gas after flotation for each sample, the flotation tail was subjected to carbon cyanidation in leaching to recover the remaining gold in the flotation tail The results are shown in the Table 12 where it is seen that the leaching of the flotation tail significantly contributes to the recovery of the gold according to the process of the present invention TABLE 12 CIL Leaching After Pressure Oxidation The present invention has been described with reference to specific embodiments thereof. According to the present, however, any of the aspects shown in the embodiments may be combined in any way with other Aspects of any other modality For example, some aspect shown in any of Figures 1-3, 8, 10-17 and 28 can be combined with any other aspect shown in any of these other Figures, although they have been described in detail of the present invention, it is evident that modifications and adaptations will occur to those modalities in those skilled in the art. It should be expressly understood that said modifications and adaptations are within the scope of the present invention established in the following claims.

Claims

CLAIMS 1 A method for the flotation processing of a feed of mineral material bearing gold containing a plurality of different species of sulfide ore, including one or more refractory gold sulfides containing gold that is refractory due to its presence in the auriferous sulfide refractory, the method comprises the steps of subjecting to flotation in a liquid medium said feeding of particulate mineral matepal, said flotation including passing bubbles of a flotation gas through the liquid medium, during flotation, a first portion of the feeding of mineral material that arises through the liquid medium with the bubbles and the first portion being collected from a flotation foam as a flotation concentrate, a second portion from the mineral material feed is collected as a flotation tail, the concentrate of flotation being enriched, in relation to the feeding of The mineral, in each plurality of different mineral species of sulfide ore, including one or more of refractory gold sulfides, and in gold, the flotation tail being devoid of, relative to the feed of mineral material, in each plurality of different sulfide mineral species, including one plus refractory gold sulfides, and in gold, wherein the flotation gas comprises an oxygen gas, if at all, at a volume fraction of oxygen gas that is smaller than the volume fraction of the oxygen gas in the ambient air, and where the flotation is substantially not selective as between said plurality of different species of sulfide ore 2 The method according to claim 1, wherein the flotation gas comprises less than about 10 percent by volume of oxygen gas 3. The method according to claim 1, wherein the flotation gas comprises less than about 5 percent by volume of oxygen gas 4 The method according to claim 1, wherein the flotation gas comprises more than about 95 percent by volume of the gas selected from the group consisting of nitrogen gas, carbon dioxide gas, helium gas, argon gas and combinations thereof The method according to claim 1, wherein the flotation gas The ion comprises combustion exhaust 6 The method according to claim 1, wherein said plurality of different species of sulfide mineral comprises a plurality of different species of sulfide mineral containing iron and the flotation is substantially non-selective to the flotation of said species of sulfide mineral containing iron, so that the flotation concentrate is rich, in relation to the feeding of mineral material, in each plurality of different sulfide mineral species containing iron The method according to claim 1, wherein after floating, said flotation tail is subjected to leaching to remove the flotation glue non-refractory gold that is not associated with a sulfide mineral The method according to claim 7 wherein the leaching comprises leaching gold cyanide from the flotation glue 9 The method according to claim 1, wherein the liquid medium comprises deoxygenated water. The method according to claim 9, wherein the deoxygenated water comprises less than about 0.2 parts per million by weight of oxygen. The method according to claim 9, in where deoxygenated water, before flotation, has been prepared by passing a gas through the water to remove oxygen from the water The method according to claim 1, wherein before the flotation with the feed of mineral material is subjected to wet grinding to reduce the particle size of mineral material, the water used during the wet grinding comprising deoxygenated water. The method according to claim 12, wherein said grinding is conducted in an environment that is substantially free of air. The method according to claim 1, wherein prior to flotation, the feed of mineral material is subjected to grinding to reduce the particle size of said material feed. mineral, the grinding being conducted in a sealed equipment to substantially prevent the air from being expelled to the equipment. The method according to claim 14, wherein the grinding comprises processing the ore material through a sealed grinding unit that the mantle gas having an inlet and outlet being introduced into at least one of the inlet and the outlet, the mantle gas comprising not more than 5 percent by volume of oxygen. The method according to claim 15 wherein the Mantle gas comprises more than 95 percent by volume of the gas selected from the group consisting of nitrogen gas, ac rbonus, helium gas, argon gas and combinations thereof The method according to claim 14, wherein starting with grinding and finishing after flotation, the feed of mineral material is processed in an environment that is substantially free of oxygen gas. The method according to claim 1 in where before flotation, the feed of mineral material is subjected to crushing to reduce the particle size of the feeding of mineral material, the grinding being performed inside a container having a non-metallic inner liner to reduce the potential for contamination of the mineral material by iron. The method according to claim 1, wherein before flotation, the feed of mineral material is subjected to grinding in the presence of grinding media to reduce the particle size of said mineral material, the grinding media comprising at least one corrosion-resistant steel and a hardened steel alloy 20 The method of agreement with claim 19, wherein the grinding media comprises at least one of stainless steel a chromium alloy steel and a nickel alloy steel. The method according to claim 1, wherein before flotation, the Mineral material feed is subjected to magnetic separation to remove the magnetic iron particles to reduce go the galvanic interaction involving iron during flotation The method according to claim 1, wherein the lead-containing activator makes contact with the mineral matepal feed during the flotation. The method according to claim 17, wherein the Activator containing lead comprises at least one lead nitrate and lead acetate The method according to claim 1, wherein a copper-containing activator makes contact with the feed of mineral material during flotation. The method according to claim 1, wherein a xanthate collector makes contact with the feed of mineral material during flotation 26 The method according to claim 1, wherein during flotation, the liquid medium is at an acidic pH. The method according to claim 1, wherein during the flotation, the liquid medium is a a pH of less than about 6 28 The method according to claim 1 wherein during flotation, the liquid medium is at a pH of about 3 about 6 The method according to claim 1, wherein the float comprises a first flotation stage of the mineral material feed to produce a first concentrate of enriched flotation, in relation to the feed n of mineral material, in sulfur species and in gold and to produce a first flotation tail devoid of, in relation to the feeding of mineral material, in the sulfide species and in gold, the flotation also comprises a second flotation stage wherein at least a portion of the first flotation tail is subjected to additional flotation to produce a second flotation concentrate rich in, relative to the first tail of flotation, said sulfur and gold species and to produce a second flotation tail devoid of, in relation to the first flotation tail, sulfur and gold species after the first flotation stage and before the second flotation stage, the The first flotation glue is subjected to grinding to reduce the particle size in the first flotation glue 30 The method according to claim 29, wherein after the grinding and before the second flotation step, the flotation glue is subjected to size separation to separate the first flotation glue into two fractions, a first fraction of particles with smaller size and a second fraction of particles with larger size, said second fraction being subjected to the second flotation stage and the fraction is not subjected to the second flotation stage 31 The method according to claim 1, wherein the flotation is conducted in a sealed flotation apparatus having an upper vapor space above the liquid medium, the gas is withdrawn from the upper vapor space and recirculated to enter the liquid medium to form at least a part of the flotation gas. according to claim 31, wherein the flotation apparatus comprises means for dispersing the flotation gas in the liquid medium, said means for dispersing creating a vacuum to suck the gas from the upper vapor space to introduce the gas to the liquid medium. The method according to claim 1, wherein one or more of the refractory auriferous sulfides includes an arsenical pint. The method according to claim 1, wherein one or more of the refractive auriferous sulfides includes an arsenical markeite. The method according to claim 1, wherein one or more of the refractory auriferous sulfides includes an arsenical pyrrhotite. The method according to claim 1, wherein one or more of the refractory auriferous sulfides includes arsenic. with claim 1, wherein one or more of the refractory auriferous sulfides includes an orpimethope containing iron 38. The method according to claim 1, wherein one or more of the refractory auriferous sulphides includes a realgar containing iron 39; according to claim 1, wherein the plurality of different sulfur mineral species includes, in addition of one or more of refractory gold sulfides, at least one sulfide species that is not a refractory gold sulfide The method according to claim 39, wherein at least one sulfide species includes a sulfide containing iron 41. The method according to claim 1, wherein the plurality of different sulfur mineral species includes a plurality of different pyrite species, a first pint species having a morphology with a coarser grain size than a second species of pyrite. pint, which has a morphology with a finer grain size, and one or more refractory auriferous sulfides includes the second pint species. The method according to claim 37, wherein the first pint species is substantially free of gold. in relation to the second pint species 43. The method according to claim 1, wherein the plurality of different sulfide mineral species includes a plurality of different species of refractory auriferous sulfides and at least one sulfide species being substantially free of sulfur. gold in relation to each of the plurality of different species of refractory gold sulfides The method according to claim 1 wherein one or more refractory auriferous sulphides includes a plurality of different refractory auriferous sulfide species, the flotation concentrate is rich in each of the plurality of different refractory gold sulfides and the tail of each of the plurality of refractory auriferous sulfides is lacking The method according to claim 44, wherein the plurality of different refractory auriferous sulfide species includes at least a plurality of different arsenical iron sulfides The method according to claim 45 wherein the plurality of different arsenical iron sulfides includes a plurality of members of the group consisting of a Arsenical pyrite an arsenical marcasite and an arsenical pyrrhotite The method according to claim 44 wherein the plurality of different refractory auriferous sulfide species includes a plurality of members of the group consisting of an arsenical pint an arsenical marcasite an arsenical pyrrhotite an arsenopyrate an iron-containing orifice and a realgar contains iron 48. The method according to claim 1 wherein the flotation is substantially non-selective as substantially all of the sulfide mineral species originally are in the feed of mineral material.