The present invention relates to a method of recovering a metal, such as copper or nickel or zinc or cobalt, from a metal sulfide-containing material in a mined material.

The present invention relates to a method of recovering a metal, such as copper or nickel or zinc or cobalt, from a metal sulfide-containing material in a mined material that is “non-eeonomic” from the perspective of recovering the metal from the material using conventional recovery options before the invention was made and, for example, is in stockpiles of “waste” material.

The term “mined material” is understood herein to include material that is mined and transferred from the mine (a) directly to downstream processing operation to recover a metal from tire material or (b) to a stockpile. The stockpiled material may be material that can be transferred to the downstream processing operation at a later time. The stockpiled material may be “waste” material that until the invention was made would not be processed later because it was “non-eeonomic” to recover metals from using conventional recovery options available before the invention was made. The term ““non-economic” to recover metals from using conventional recovery options” is understood to mean processing options used in commercial mines before the invention was made.

The present invention relates particularly, although by no means exclusively, to a heap leaching method that is characterized by leaching a heap of agglomerates of a metal sulfide-containing material and pyrite, typically pyrite that is available in a mine, such as pyrite derived from mine tailings from a processing plant for recovering metal from a metal sulfide-containing material, such as a metal sulfide mineral.

The present invention also relates to a heap leaching operation that includes a heap containing agglomerates of a metal sulfide-containing material and pyrite, typically pyrite that is available in a mine, such as pyrite derived from mine tailings from a processing plant for recovering metal from a metal sulfide-containing material, such as a metal sulfide mineral.

The present invention also relates to a flotation circuit for an ore processing plant for a metal sulfide -containing material, with the flotation circuit producing a source of pyrite. The present invention also relates to an ore processing plant for a metal sulfide- containing material.

BACKGROUND ART The technical field of the invention is the production of a metal, such as copper or nickel or zinc or cobalt, from a metal sulfide-containing material, such as a metal sulfide mineral, in a mine.

The following description of the invention focuses on copper as one example of a metal in a metal sulfide -containing material, such as a metal sulfide mineral. Copper is an increasingly important metal for the transition to a low carbon-based global economy.

There are substantial capital and operating cost pressures on mine operators of well- established and new copper mines (which term includes mines in which copper is the only metal recovered and mines in which copper and other valuable metals such as gold are recovered) that have lower average concentrations of copper in copper sulfide-containing materials than was previously the case.

In many instances, the problem of lower copper concentrations in copper sulfide- containing materials, such as copper sulfide-containing minerals, is compounded by the copper being in more refractory copper sulfide-containing minerals than previously, with these minerals being more difficult and expensive to process to recover copper from the minerals.

Mining companies are also very conscious of the importance of operating mines with minimal environmental impact over short and longer terms.

The economics facing copper mine operators mean that there are substantial amounts of copper sulfide-containing material, including mined material and processed forms of mined material (he, comminuted), that are non -economic to recover copper from using recovery options available before the invention was made and therefore are not processed to recover copper from copper sulfide-containing material.

Non -economic copper sulfide -containing material is typically stored in stockpiles that are often described as waste rock stockpiles.

The concentration of copper in non-economie copper sulfide-containing material is not an absolute fixed value and will vary from mine to mine and also in an individual mine over time, having regard to capital and operating costs in the mine and factors external to the mine, such as the overall market for copper. The invention provides a method of recovering copper from copper sulfide-containing material, including copper sulfide -containing material, in a mined material that were regarded as “non-economic” to recover metals from using conventional recovery options before the invention was made. The invention provides a method of recovering other metals, such as nickel or zinc or cohalt, from metal sulfide-containing material, including metal sulfide-containing material, in a mined material that were regarded as '‘non-economic” to recover metals from using conventional recovery options before the invention was made.

The above description is not an admission of the common general knowledge in Australia or elsewhere.

SUMMARY OF THE DISCLOSURE

The invention is concerned with maximizing the beneficial use of material produced in a mine that contains metal sulfide-containing material, such as a copper mine that contains copper sulfide-containing material, but equally a nickel, zinc or cobalt mine or a mine producing two or more of these metals, from metal sulfide-containing material in a mined material, and minimizing the extent to which processing materials, such as reagents, from outside the mine are required.

One advantage of the invention is to provide an opportunity to maximize the recovery of a metal, such as copper or nickel or zinc or cobalt, from a mine that contains a metal sulfide-containing material in a mined material and to minimize the costs to do so.

Another advantage of the invention is to provide an opportunity to minimize the environmental impact of the mine.

In broad terms the invention provides a method of recovering a metal, such as copper, nickel or zinc or cobalt, from a metal sulfide-containing material in a mined material, such as a metal sulfide-containing material that is “non-economic” to recover metals from using conventional recovery options, that includes the steps of:

(a) mixing (i) the metal sulfide-containing material and (ii) pyrite and forming agglomerates; (b) leaching agglomerates from step (a) with a leach liquor and microbes and removing a metal from the metal sulfide-containing material and forming a pregnant leach liquor containing metal, with pyrite generating acid and heat and the acid facilitating leaching metal from the metal sulfide-containing material, and with the microbes oxidising ferrous iron to ferric iron; and (c) recovering metal from the pregnant leach liquor.

In more particular terms, although by no means exclusively, the invention provides a method of recovering copper from a copper sulfide-containing material in a mined material, such as a copper sulfide-containing material that is “non-economie” to recover copper from using conventional recovery options before the invention was made, that includes the steps of:

(a) mixing (i) the copper sulfide-containing material and (ii) pyrite and forming agglomerates;

(b) leaching agglomerates from step (a) with a leach liquor and m icrobes and removing copper from the copper sulfide-containing material and forming a pregnant leach liquor containing copper, with pyrite generating acid and heat facilitating leaching copper from the copper sulfide-containing material, and with the microbes oxidising ferrous iron to ferric iron; and

(c) recovering copper from the pregnant leach liquor. The metal sulfide-containing material may be derived from any suitable mined material.

As noted above, the term “mined material” is understood herein to include material that is mined and transferred from the mine (a) directly to downstream processing operation to recover a metal from the material or (b) to a stockpile and processed later. The metal sulfide-containing material may be a metal sulfide -containing material that is “non-economic” to recover metals from using conventional recovery options.

The metal may be any suitable metal.

Examples of suitable metals are copper, nickel and zinc and cobalt.

The metal may be copper. In that event, by way of example, the metal sulfide-containing material may be a copper sulfide -containing material.

The copper sulfide-containing material may be any suitable copper sulfide-containing material, such as a copper sulfide mineral.

One example of the copper sulfide-containing material is rocks that contains low concentrations of copper and, for example, may be regarded as waste rock.

The copper sulfide-containing material may be in the form of as-mined material or waste stockpiles of copper sulfide-containing material having low grades, i.e. low concentrations, of copper in the material. In other words, the copper sulfide-containing material may be as-mined material or stockpiled material that is considered to be too low grade to be economically processed in flotation and other wet processing systems for recovering copper from copper-containing ores and concentrates. The term flow grade” as used in relation to ‘‘copper sulfide-containing material” mentioned above is understood herein to be a term that is dependent on currently available technology and the current price of copper, and that material currently considered “low grade” may be considered valuable material in the future depending on technological developments and the future price of copper. More particularly, the copper sulfide-containing material may he as-mined material or stockpiled material that is too low-grade to be economically processed by any other processing method, including heap leaching.

In the context of the preceding paragraphs, the term “low concentrations of copper” is understood to mean an average copper concentration of < 1.5% by weight, typically < 1.2 wt.%, more typically < 1.0 wt.%, even more typically < 0.7 wl.%, even more typically < 0.5 wt.%, even more typically < 0.3 wt.%, even more typically < 0.1 wt.%.

The metal sulfide-containing material may he in any suitable form for the agglomeration step.

The metal sulfide-containing material may be in the form of as-mined material or stockpiled materi al that has been processed to be suitable for the agglomeration step.

The method may include comminuting as-mined or stockpiled material and producing a suitable particle size distribution for the agglomeration step.

The comminuting step may include crushing as-mined or stockpiled material in one or more than one comminution circuit that reduces the size of the material. The comminuting step may include crushing as-mined or stockpiled material successively in primary, secondary and tertiary comminution circuits, as these terms are understood by persons in the copper mining industry.

The comminuting step may include single or multiple crushing steps delivering crushed as-mined or stockpiled material to produce the material with a desired particle size distribution for the agglomeration step.

The pyrite may be 1 - 10 wt.% of the total mass of the metal sulfide-containing material and pyrite.

The pyrite may he obtained from any suitable source.

Typically, the pyrite source is from the mine. For example, the pyrite may be in tailings, i.e. a pyrite-containing slurry, from a tailings dam or an ore processing plant, of the mine with the slurry being used directly in the agglomeration step.

The term '‘ore processing plant” is understood herein to mean any suitable plant for recovering a metal from a mined ore.

The word “ore” is understood herein to mean a natural rock or sediment that contains one or more valuable minerals, typically containing valuable metals, that can be mined, treated and sold at a profit.

By way of further example, the pyrite may be obtained by removing pyrite from a pyrite-containing slurry from a tailings darn or an ore processing plant of the mine and using the removed pyrite in the agglomeration step.

Typically, the pyrite removed from the pyrite-containing slurry is in a concentrate form.

The method may include a pyrite removal step for removing pyrite from a pyrite - containing slurry , for example from a tailings dam or an ore processing plant, and forming an inert stream - i.e. a stream that is less reactive than the input tailings to the pyrite removal step in terms of the amount of pyrite in the inert stream.

The pyrite-containing slurry may be processed in the pyrite removal step, for example by being beneficiated, by any method that recovers and concentrates pyrite from the slurry. The pyrite removal step may include floating pyrite-containing material in the pyrite- containing slurry and producing (i) an inert stream as one flotation output and (ii) a pyrite- containing material stream, such as a pyrite-containing concentrate stream, as another flotation output.

The pyrite removal step may include, before the above flotation step, a size separation step, such as via cyclones or other suitable classification devices, that for example separates larger particles from the pyrite-containing slurry, with the remaining pyrite-containing slurry being transferred to the flotation step.

The term “cyclone” is understood herein to describe a device that can classify, separate or sort particles in a liquid suspension based on the ratio of their centripetal force to fluid resistance. This ratio is high for dense ('where separation by density is required) and coarse (where separation by size is required) particles, and low for light and fine particles.

The pyrite removal step may include reducing the size of the larger particles in a size reduction circuit and returning the reduced-sized particles to the size separation step. The pyrite removal step may include selecting the operating conditions for the size separation step so that pyrite particles in the pyrite-containing material in the remaining pyrite-containing slurry have a required particle size distribution for downstream processing of the tailings, for example in a heap leaching operation. The pyrite removal step may include thickening and/or filtering the pyrite-containing material stream and de- watering the stream and forming a pyrite-containing concentrate.

The above-described method has the following advantages:

• The method makes it possible to extract a metal such as copper or nickel or zinc or cobalt from a metal sulfide-containing material that is “non-economie” from the perspective of recovering the metal from the metal sulfide-containing material.

• When the pyrite is in tailings (i.e. pyrite-containing slurry), the method makes it possible to process tailings that contain pyrite and thereby reduce the volumes of existing tailings dams. This is an important environmental outcome.

• The acid and heat generating capacity of pyrite is an ad vantage in leaching, such as heap leaching, and, for example, can reduce the amount of added acid that is required in the leach liquor.

• Moreover, the acid-generating capacity of pyrite means that tire pyrite is used beneficially in the leach step and results in a net reduction in pyrite, which is significant from an environmental perspective. * It is noted that any amounts of the metal, such as copper, nickel and zinc and cobalt, in the pyrite-containing material is a bonus - it is taken into the heap with pyrite and can be recovered in the heap leaching step.

• In addition to producing the above-mentioned pyrite, removing pyrite from tailings produces an inert stream - i.e. a stream that is less reactive than the input tailings to the pyrite removal method in terms of the amount of pyrite in the inert stream. This is beneficial because pyrite in tailings is an environmental problem because pyrite makes the tailings “acid generating tailings'’ and this is an issue for disposal of the tailings.

• The option of adding the pyrite-containing slurry directly in agglomeration if it contains sufficient pyrite so that a pyrite removal step is not necessary, is an efficient use of these tailings.

• The method can be operated with readily-available and tried and tested equipment. • The method makes it possible to process what has been previously classified as waste materials, namely metal sulfide-containing material and tailings, and reduce tire environmental impact of these materi als as well as optimising the recovery of value from tiie originally-mined material. The agglomeration step may be any suitable step for agglomerating the metal sulfide- containing material, such as a copper sulfide-containing material, and the pyrite-containing material.

The agglomeration step may include mixing and agglomerating the metal sulfide- containing material, such as a copper sulfide-containing material, and the pyrite-containing material.

The pyrite particles in the pyrite-containing material may have a particle size of Pgo of 1 mm or a value < 1 mm.

The pyrite particles in the pyrite-containing material may have a particle size of Pgo of 250 pm or a value < 250 pm. The mixing step may he carried out before the agglomerating step.

The mixing and the agglomerating steps may be carried out simultaneously.

The leaching step may be any suitable leaching step.

The leaching step may be a heap leaching step.

The leaching step may include any suitable heap leaching steps that leach metal, such as copper or nickel or zinc or cobalt, from the metal sulfide-containing material in the heap of the agglomerates and recovers metal into solution.

In broad terms, the invention also provides a heap leaching method for a metal sulfide-containing material that contains a metal, such as copper or nickel or zinc or cobalt, or contains two or more of these metals, in a metal sulfide-containing material, the method comprising:

(a) leaching a heap of agglomerates of the metal sulfide-containing material and pyrite with a leach liquor, with the pyrite generating acid and heat that facilitates leaching metal from the metal sulfide-containing material and producing a pregnant leach liquor containing the metal in solution, typically with the pyrite being in or derived from a slurry containing pyrite, such as mine tailings, and with the microbes oxidising ferrous iron to ferric iron; and

(b) collecting the pregnant leach liquor from the heap.

The heap leaching method also comprises recovering the metal from the pregnant leach liquor. The present invention also provides a heap leaching operation for leaching a metal, such as copper or nickel or zinc or cobalt, from a metal sulfide -containing material in a mined material, the heap leaching operation comprising:

(a) a heap of agglomerates of the metal sulfide-containing material and pyrite: and (b) a system that (i) supplies leach liquor and microbes to the heap so that the leach liquor flows downwardly though the heap and leaches the metal from the metal sulfide- containing material and (ii) collects a pregnant leach liquor containing the metal in solution from the heap, with the pyrite generating acid and heat in the heap that facilitates leaching the metal from the metal sulfide-containing material, with pyrite being in or derived from a slurry containing pyrite, such as mine tailings, and with the microbes oxidising ferrous iron to ferric iron.

The metal sulfide-containing material may he derived from any suitable mined material.

As noted above, the term “mined material” is understood herein to include material that is mined and transferred from the mine (a) directly to downstream processing operation to recover a metal from the material or (b) to a stockpile and processed later.

In broad terms, the invention also provides a method of mining comprising:

(a) mining a metal sulfide-containing material, such as a copper-sulfide containing material; and (b) the above-described method of recovering a metal, such as copper, nickel or zinc or cobalt, from the metal sulfide-containing material that is categorized by a mine operator as being “non -econom ic” from the perspective of recovering the metal from the material.

The method may include processing metal sulfide -containing ore in the metal sulfide- containing material in an ore processing plan! and producing a pyrite-containing slurry for step (b).

The present invention also provides a flotation circuit for an ore processing plant for a metal sulfide-containing material, the flotation circuit including:

(a) a mill feed flotation circuit for producing a tailings stream and a concentrate stream from a mill feed, with the tailings stream comprising a metal sulfide- containing material; and

(h) a pyrite flotation circuit for producing a pyrite concentrate stream, i.e. a pyrite- containing slurry, and a tailings stream. The pyrite concentrate stream may be a source of pyrite for the above-described method of recovering a metal, such as copper, nickel or zinc or cobalt, from a metal sulfide- containing material.

The pyrite flotation circuit may be configured to process the pyrite concentrate stream, i.e. a pyrite-containing slurry , in accordance with the above-described pyrite removal step and producing (i) the tailings stream as the inert stream and (si) the pyrite concentrate stream as the pyrite-containing material stream.

The mill feed flotation circuit may he any suitable circuit.

The mill feed flotation circuit may include a rougher/scavenger cell and a hulk cleaner ceil. These may be standard rougher/scavenger and bulk cleaner cells. These may he existing cells in an ore processing plant. They may be cells in a greenfield plant.

The rougher/scavenger and tire bulk cleaner ceils may be configured so that: (i) tire rougher/scavenger cell processes the mill feed and produces a first tailings stream and a concentrate stream and (ii) the bulk cleaner cell processes the concentrate stream and produces a second tailings stream and another concentrate stream and transfers the other concentrate stream for further processing, such as metal recovery, and the second tailings stream to the pyrite flotation circuit for processing in that circuit.

The metal sulfide-containing material may he a copper sulfide-containing material, such as a copper sulfide -containing mineral. The mill feed may be any suitable particle size distribution of the metal sulfide- containing material.

The ore processing plant may include any suitable upstream comminution circuits for producing the mill feed and downstream recovery and tailings storage of other options.

The present invention also provides an ore processing plant for a metal sulfide- containing material comprising the above flotation circuit.

The ore processing plant may also include any suitable upstream comminution circuits and downstream recovery and tailings storage and/or treatment options.

The metal sulfide-containing material may be a copper sulfide-containing material, such as a copper sulfide-containing mineral.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described further below by way of example only with reference to the following Figures, of which: Figure 1 is a flow sheet of one embodiment of a method of processing, for example by beneficiating, pyrite-containing tailings, i.e. a pyrite-containing slurry, and using the pyrite removed from the tailings in downstream heap leaching of a copper sulfide-containing material; Figure 2 is a graph of copper extraction versus leaching time for a series of column bioleach tests conducted on (i) a sample of ore from a copper mine, (ii) the copper ore augmented with finely pulverised museum grade pyrite and (iii) the copper ore augmented with pyrite concentrate produced by flotation of tailings produced at the copper mine; and

Figure 3 is a flow sheet of one embodiment of a flotation circuit for an ore processing plant in accordance with the invention.

DESCRIPTION OF EMBODIMENTS

One embodiment of the invention described below is described in the context of recovering copper from a copper sulfide-containing material from a mine.

It is noted that the invention is not confined to copper and extends to other metals such as nickel or zinc or cobalt, in metal sulfide-containing materials from a mine.

In general terms, the embodiment shown in Figure 1 is a method of mining comprising:

(a) mining and optionally stockpiling a copper sulfide-containing material, such as a copper sulfide-containing mineral;

(b) processing a copper sulfide-containing ore, as described herein, in the copper sulfide-containing material in an ore processing plant and (i) recovering copper and (ii) producing a pyrite-containing slurry;

(c) processing the pyrite-containing slurry and producing pyrite; and

(d) processing “non-economic” copper sulfide-containing material, as described herein, with pyrite in a heap leaching operation.

In more specific terms, the heap leaching operation shown in Figure 1 includes the steps of:

(a) processing a slurry containing pyrite from a tailings dam or tire ore processing- plant (not shown) of the mine and removing pyrite therefrom;

(h) forming agglomerates of the copper sulfide-containing material and pyrite from step (a);

(c) leaching the agglomerates, with pyrite facilitating recovery of copper from the copper sulfide-containing material, and forming a copper-containing liquor; and (d) recovering copper from the copper-containing liquor.

It is noted that the pyrite- containing slurry may be any suitable pyrite-containing slurry, such as tailings, from an ore processing plant. Example 2 and Figure 3 describe an embodiment of a flotation circuit in accordance with the invention for producing a suitable pyrite-containing slurry.

The “noil-economic” copper sulfide-containing material is described in relation to Figure I in the context of waste rock, i.e. material that is “non-economic” to recover metals from using conventional recovery options, i.e. processing options used in commercial mines before the invention was made. The material may be as-mined material or stockpiled material. Typically, the copper concentration of the waste rock is < 1.5% by weight, typically < 1.2 wt.%, more typically < 1.0 wt.%, even more typically < 0.7 wt.%, even more typically < 0.5 wt.%, even more typically < 0.3 wt.%, even more typically < 0.1 wt.%.

In addition, the embodiment of the method of recovering copper from a copper sulfide-containing material in accordance with the invention shown in Figure 1 is described in the context of the pyrite being a pyrite concentrate extracted from mine tailings.

It is understood that the invention is not confined to this embodiment and extends generally to any suitable copper-containing material and to any suitable source of pyrite.

Processing the copper-containing material prior to forming agglomerates - steps 1, 2. 3 In the flow sheet shown in Figure 1, the copper sulfide-containing material is in the form of waste rock 1 that has been re-mined from stockpiles 1.

As noted above, currently, these waste rock stockpiles are considered too low grade to be economically processed for recovering copper by known conventional methods.

As noted above, the invention is not confined to this source of copper sulfide- containing material.

For example, the copper sulfide -containing material may be material that is considered too low grade to be economically processed for recovering copper by known conventional methods in test work carried out on a section of a mine before being mined (for example by drilling and blasting) and then, after mining, is transferred directly from the mine (without being stockpiled) for processing in steps 2 and 3.

The stockpiled waste rock 1 is transported in suitable vehicles, such as haul tracks or front-end loaders, for crushing and milling successively in primary, secondary and tertiary comminution circuits 2, 3 to the extent required to produce a suitable particle size distribution for the agglomeration step 4. The comminution circuits 2, 3 may include single or multiple crushing steps delivering crashed copper-containing material to single or multiple milling and sizing steps to produce the comminution product stream having a desired particle size distribution for the agglomeration step 4. The crashing steps 2, 3 may be carried out using any suitable combination of gyratory, cone and high pressure grinding roll (HPGR) crushers (not shown in the Figures).

The resultant comminuted copper sulfide-containing material is transferred to the agglomeration step 4. Agglomeration step 4

The agglomeration step 4 agglomerates:

(a) the comminuted copper sulfide -containing material produced in steps 2 and 3; and

(b) pyrite that, in this embodiment, is tailings-derived pyrite -containing concentrate (see below). The agglomeration step 4 may be any suitable agglomeration step using any suitable apparatus, such as agglomeration drums.

By way of example, required ratios of the comminuted copper sulfide-containing material and the pyrite-containing concentrate are added to a mixing device and are mixed together, with or without a binder, with or without an acid, and with or without added water, and with or without recycled leach solution.

The required ratios depend on factors such as the amount of pyrite in the rock. Typically, a broad pyrite concentration range for tire mixed product is from 1 - 10 % pyrite.

The selection of the binder and the acid and the addition of water and/or recycled leaching solution are a function of a number of factors, including the characteristics of the com minuted copper sulfide-containing material and the pyrite-containing concentrate and the required mechanical properties for the agglomerates.

The agglomeration step 4 may include any suitable protocol for adding and mixing the comminuted copper sulfide-containing material and the pyrite-containing concentrate and the hinder and water, if required. The agglomerates are stored in a stack 5 and are transferred to the heap leach steps described below.

Heap and downstream solvent extraction and electrow inning steps 5, 6, 9, 10, 11, 12

The agglomerates from the stack 5 are formed into a heap 6 on a leach pad. The heap 6 may be any suitable heap construction and is provided with:

(a) a leach liquor storage and delivery system to supply leach liquor to an upper surface of the heap;

(h) a pregnant leach liquor collection system for collecting leach liquor containing copper in solution that is extracted from copper sulfide-containing materials in agglomerates in the heap; and

(c) microbes (such as bacteria or archaea) or other suitable oxidants to oxidise ferrous iron to ferric iron, with the ferric iron being an oxidant in the leaching process.

The pregnant leach liquor is processed in a solvent extraction system 9 that extracts copper from the liquor in an organic medium and then strips copper from the organic medium and produces a copper-containing solution.

The copper-containing solution is transferred to an electro winning plant 10 and copper is recovered from solution.

The raffinate from the solvent extraction system 9 is regenerated and returned to returned to the heap as leach liquor. The leach liquor regeneration system includes a raffinate bleed limestone/lime neutralization 11 to control the build-up of impurities, generating neutralized solids for separate impoundment or possibly co-impoundment with tailings.

The pyrite-containing concentrate in the agglomerates provides valuable sources of acid via the pyrite and heat. The acid-generating properties of the pyri te mean that the amount of acid that has to be added to the leach liquor can be reduced to maintain a given leaching acid requirement.

In addition, the microbial oxidation of pyrite produces acid and heat, all of which are beneficial for heap leaching the copper sulfide-containing material. Separation steps 15, 16, 17. 18, 19, 20 for pyrite-containing tailings

As noted above, the pyrite for the agglomeration step 4 is mine tailings.

Typically, the tailings are an output of an ore processing plant for recovering copper from a copper sulfide-containing ore that contains copper sulfide-containing material, such as copper sulfide minerals. The ore processing plant may be any suitable plant.

One example of an ore processing plant is one that includes comminution of mined ore involving a series of crushing and grinding stages and one or more than one flotation circuit for floating copper sulfide minerals from the comminuted ore (described above and in Example 2 as a “mill feed”) and producing a valuable concentrate output and a tailings output (a pyrite-containing slurry).

Typically, the solids in the tailings are in the form of a slurry of (a) fines, with low concentrations of copper, typically less than 0.4 wt.%, more typically less than 0.3 wl.%, and (b) pyrite-containing particles suspended in water. Typically, these fines and pyrite- containing particles are slow to settle. The pyrite-containing particles may also contain some copper.

The tailings are transferred, for example by being pumped, from a tailings dam or other suitable source of tailings 15, such as directly from the ore processing plant, to a series of cyclones 16 or any other suitable size separation option that separates larger solids from the remaining fines-eontaining tailings.

The cyclones 16 may be any suitable cyclones.

The larger solids stream from the cyclones are processed in a size reduction circuit, such as a millmg/grinding/polisbing circuit 17. The output of tins circuit is returned to the cyclones 16 for further processing in the cyclones.

The operating conditions of the cyclones are selected so that the remaining tailings have a required particle size distribution for the heap leach step 5. In this regard, typically pyrite-containing particles in the remaining tailings have a particle size of !¾ of 1 mm or a value < 1 mm. More typically, pyrite particles in the remaining tailings have a particle size of Pgo of 250 pm or a value < 250 pm.

The remaining tailings from the cyclones 16 are transferred to a 1 ^st flotation circuit 18 (described in Example 2 in relation to Figure 3 as a “pyrite flotation ceil”) and are processed in the circuit. Suitable flotation reagents are added to the circuit as required. The operating conditions, including reagents, are selected to float pyrite-containing particles. Typically, these operating conditions will also float copper particles.

The underflow from the 1 ^st flotation circuit forms the abovementioned inert stream.

As noted above, the term “inert” means that the stream is less reactive than the input slurry to the method in terms of the amount of pyrite in the stream. In the context of Figure 1 this means that the underflow stream is less reactive than the pyrite-containing tailings supplied to the method in terms of the amount of pyrite in the stream. As noted above, this is beneficial because pyrite in tailings is an environmental problem because pyrite makes the tailings “acid generating tailings” and this is an issue for disposal of the tailings. The method provides an opportunity to produce an output that is environmentally safe for use in downstream applications, such as in copper ore processing plants, and can reduce the oxidant (ferric iron) requirements. The ferric iron (produced by microbial oxidation of the ferrous iron that dissolves from the pyrite concentrate and iron-bearing minerals in the waste rock) oxidizes the pyrite and the copper sulfide minerals. In the embodiment of Figure I, the underflow stream for the 1 ^st flotation circuit is transferred to a downstream neutralization step 11 described below.

The overflow, i.e. the floated stream from the l ³ⁱ flotation circuit is transferred to and processed in a 2 ^nd flotation circuit 19 (described in Example 2 in relation to Figure 3 as a “pyrite flotation cell”). The 2 ^nd flotation circuit 19 processes the floated stream from the l ^si flotation circuit.

Suitable flotation reagents are added to the circuit as required. The operating conditions, including reagents are selected to float pyrite -containing particles.

The underflow from the 2 ^nd flotation circuit is transferred back to the 1 ^st flotation circuit. The pyrite-eontaining floated stream from the 2 ^nd flotation circuit is transferred to thickeners 20 and de-watered and forms a pyrite-eontaining concentrate.

The pyrite-eontaining concentrate is transferred from the thickeners 20 to the agglomeration steps 4, 5 described above.

It is noted that, whilst the described embodiment has two flotation circuits 18, 19, the invention is not confined to this number of circuits.

It is also noted that, whilst the described embodiment includes cyclones 16 and a miliing/grinding/polishing circuit 17 and returns material to the cyclones 16, the invention is not confined to this arrangement.

For example, the combination of the cyclones 16 and the miliing/grinding/polishing circuit 17 would not be necessary if the particle size distribution in the tailings supplied from the tailings dam or other suitable source of tailings 15 is suitable for downstream processing- after the separation steps.

By way of further example, the combination of the cyclones 16 and the miliing/grinding/polishing circuit 17 would not be necessary where there are downstream steps to optimize the particle size distribution of pyrite particles in the pyrite-eontaining concentrate.

Advantages of the embodiment shown in Figure 1 The advantages of the above-described embodiment shown in Figure I, and the invention generally, include the following advantages:

• The method makes it possible to extract copper from a copper sulfide-containing material, such as a copper sulfide-containing material that has been categorized by a mine operator as being “non -economic” from the perspective of recovering copper from the material.

• The method makes it possible to process tailings and thereby reduce the volumes of existing tailings dams. This is an important environmental outcome. Tailings present significant environmental and safety risks during the lives of mines. There are substantial issues involved in maintaining tailings dams and remediating tailings dams at the end of the lives of mines. In addition, there are potential issues with structural integrity of tailings dams. From time to time, there are catastrophic collapses of tailings dams that have caused loss of life and considerable damage to areas downstream of the dams. Also, tailings often contain contaminants (such as pyrite) which present challenges for mine remediation. Pyrite in tailings poses a potential environmental hazard because the tailings can oxidize to produce an acidic effluent that requires treatment to neuhalize the acidity and remove contaminants before it can be discharged.

• The acid and heat generating capacity of pyrite is an advantage in leaching, such as heap leaching, and, for example, can reduce the amount of added acid that is required in the leach liquor.

• Moreover, the acid-generating capacity of pyrite means that the pyrite is used beneficially in the leach step and results in a net reduction in pyrite, which is significant from an environmental perspective. ® It is noted that any amounts of copper in the pyrite-containing material is a bonus - it is taken into the heap with pyrite and can be recovered in the heap leaching step.

• In addition to producing the ahovementioned pyrite, removing pyrite from tailings produces an inert stream - i.e. a stream that is less reactive than the input tailings to the pyrite removal method in terms of the amount of pyrite in the inert stream. This is beneficial because pyrite in tailings is an environmental problem because pyrite makes the tailings “acid generating tailings” and this is an issue for disposal of the tailings.

• The method can be operated with readily-availabie and tried and tested equipment. • The method makes it possible to process what has been previously classified as waste materials, such as low-grade copper -containing material or waste rock and tailings, and reduce the environmental impact of these materials as well as optimising the recovery of value from the originally-mined material.

Example 1

The applicant has carried out column bioleach tests to investigate the impact of pyrite augmentation on bioleaching of a copper ore.

The column bioleach tests evaluated copper extraction versus leaching time for (i) a sample of ore from a copper mine, (ii) the copper ore augmented with finely pulverised museum grade pyrite and (iii) the copper ore augmented with pyrite concentrate produced by flotation of tailings produced at the copper mi ne.

A sample of ore from a copper mine was crushed to <12 mm, with a Pso of 9 mm and around 10 kg of this material was added to an agglomerating drum with water and concentrated sulfuric acid.

In tests with added pyrite, either nearly pure museum grade pyrite, or fine pyrite concentrate produced by flotation of tailings produced at a copper mine, was mixed with the ore in the agglomerating drum to increase, or augment, the pyrite content of tire agglomerated material from 0.86 wt.% pyrite naturally present in the ore to 4.0 % pyrite. Both pyrite samples used were very line with a Pioo of 150 pm. The samples were subjected to elemental and mineraiogicai analysis.

It is noted that the term “museum grade pyrite’’ is understood herein to mean a pyrite content of greater than 90 wt.%, typically greater than 95 wt.%, typically greater than 97 wt.%, or more typically greater than 99 wt%. Museum grade pyrite may have a silver content of less than 1 mg/kg, typically less than 0.5 mg/kg, typically less than 0.2 mg/kg, or more typically less than 0.1 mg/kg.

Table 1 summarises the elemental and mineraiogicai compositions of the ore, the museum grade pyrite and the pyrite concentrate used in the tests. Table 1: Major elements and sulfide minerals in the ore and pyrite samples.

Once mixed, the agglomerated material was loaded into 1 m high, 0.1 m diameter columns and allowed to cure for 2-5 days at room temperature before leaching commenced. During leaching, the temperature of the columns was controlled at 50 °C using a heating jacket and the column was aerated at 0.102 NnTVh/ionne ore. The column was inoculated with ferrous iron-oxidising and sulfur-oxidising microorganisms and the irrigation solution, which initially contained 5 g/L ferric iron as ferric sulfate, was pumped into the top of the column through drippers, at 10 L/h/m ² , and collected at the base of the column.

The pH of the collected leach solution was adjusted to the target pH of 1.2 with sulfuric acid if required before recycling back to the top of the column. Solution samples were regularly taken for analysis of their metals and sulfate concentrations.

The irrigation solution had a sulfate concentration of about 20 g/L at the beginning of the leach. If the sulfate concentration in solution exceeded 120 g/L, due to addition of sulfuric acid and oxidation of the sulfide minerals, the solution was diluted to maintain a maximum of 120 g/L sulfate.

If the solution copper concentration exceeded 8 g/L, due to copper leaching, the solution was subjected to ion exchange to remove copper and reduce the solution copper concentration to maintain it at less than 8 g/L.

The column tests were under leach for 350 days. Upon completion of leaching, the columns were rinsed first with dilute sulfuric acid and then with water to remove dissolved metals and sulfate contained in the entrained leach solution. The columns w'ere then emptied and the solids dried and assayed along with the final leach solution. Mass balances were conducted and the copper extraction reported on the basis of the calculated copper head assay. Figure 2 is a graph depicting copper extraction versus leaching time for the three column tests and Table 2 summarises the copper and sulfide mineral extractions achieved. Table 2: Column test extraction results.

The beneficial effect of augmenting die ore with pyrite on copper extraction is clearly evident from Figure 2 and Table 2.

Copper extraction was increased by 11.5% and 14.4 % by adding museum grade pyrite and pyrite concentrate respectively. The enhanced copper extraction is believed to be attributable to the increased availability of ferric iron provided by the oxidation and leaching of the added pyrite, which reacted rapidly due to its fine particle size (Pioo of 150 pm). This is evident from the pyrite extraction results shown in Table 2. Extraction of pyrite in the ore was only 50.0 % whereas extraction of pyrite from the ore augmented with the museum grade pyrite and pyrite concentrate was much higher, reaching 90.2 % and 89.4 % respectively.

Notably, copper extraction was very high from the minus 150 pm fines fraction in all three tests; 87.1% in the test on the ore, 90.2 % in the test on the ore augmented with museum grade pyrite, and 92.0 % in the test on the ore augmented with pyrite concentrate. The results demonstrate that very high copper extraction was achieved from the copper minerals contained in the ore fines as well as the copper minerals in the two pyrite augments, both of which had a Pioo particle size of minus 150 pm. The natural silver content of the column feed samples, expressed in Table 2 as g Ag/kg CuFeS?, is believed to have had a beneficial catalytic effect and enhanced the recovery of copper from chalcopyrite (as taught in International application PCT/AU2018/050316 (WO 2018/184071) in the name of the applicant), particularly from the chalcopyrite in the fines fractions. Thus, the invention provides a means of achieving very high copper extraction from copper minerals contained in the pyrite augment as well has high copper extraction from copper minerals contained in an ore. Example 2

The purpose of Example 2 is to show the effectiveness of removing pyrite from a pyrite-containing slurry produced in a flotation circuit in an ore processing plant.

Figure 3 is a flow sheet of one embodiment of a flotation circuit 23 for an ore processing plant in accordance with the invention. The ore processing plant may include any suitable upstream comminution circuits and downstream recovery and tailings storage or other options (not shown).

The flotation circuit 22 shown in Figure 3 includes a rougher/scavenger cell 25 and a bulk cleaner cell 27. These may be standard rougher/scavenger and bulk cleaner ceils. These may be existing cells in an ore processing plant. They may be cells in a greenfield plant. The flotation circuit 22 shown in Figure 3 also includes a pyrite flotation cell 29 of the type described above in relation to Figure 1, noting that Figure 1 includes two ceils 18, 19 and Figure 3 shows a single cell 29. It is noted that the invention extends to any suitable number of pyrite flotation cells, with size separation and re-grind options 16, 17 and other options for processing a feed material to the cells for example as illustrated in Figure 1, as may be required.

In use, a mill feed 31 is transferred to the rougher/scavenger cell 25, and the cell produces a concentrate stream 33 and a first tailings stream 35. The mill feed 31 may be any suitable mill feed, produced for example by combinations of crashing and grinding and size separation steps, which may be existing comminution circuits in an ore processing plant or purpose-designed circuits in a greenfield plant.

The first tailings stream 35 is transferred to an impoundment location 37. This may be a tailings dam or other tailings treatment options.

The concentrate stream 33 from tire rougher/scavenger cell 25 is transferred to the bulk cleaner ceil 27, and the cell produces a plant concentrate stream 39 and a second tailings stream 41.

The plant concentrate stream 39 from the bulk cleaner cell 27 is transferred for recovery of copper and other metals such as molybdenum. The recovery options may be any suitable options. The second tailings stream 41 from the bulk cleaner cell 27 is transferred to the pyrite flotation cell 29, and the cell produces a pyrite -containing concentrate stream 43 and a third tailings stream 45.

The first and third tailings streams 35, 45 and, optionally, a part of the second tailings stream 41, are transferred to the impoundment location, such as tailings storage or other tailings treatment options.

The pyrite-containing concentrate stream 43 is transferred for further processing, such as agglomeration, and use in the above-described heap leaching circuit as shown in Figure 1.

The applicant carried out large-scale flotation testwork on a sample of a scavenger/cleaner tailings, i.e. the second tailings stream, in the pyrite flotation cell shown in Figure 3. The results are described below.

Table 3 summarises the composition of the pyrite concentrate obtained from a feed of scaveiiger/cieaiier tailings, i.e. the second tailings stream, in the pyrite flotation cell.

The table shows the effectiveness of recovering of pyrite (and copper minerals - which is a considerable advantage) in the pyrite concentrate stream (see rows 1-10) from tailings using flotation.

The process produced a pyrite concentrate at a grade of 83% pyrite, 2.2% Cu and a rougher/scavenger tails at a pyrite grade less than 0.8 % pyrite.

Table 3: QEMSCAN bulk mineralogy of Cleaner Scavenger Tails sample (the second tailings stream 41) and Pyrite Concentrate from the pyrite flotation cell 29

Table 4 provides a summary of key results from the large-scale pyrite flotation testwork and shows that 78 wt.% of the pyrite originally contained in the tailings sample was recovered to the pyrite concentrate.

Table 4: Pyrite Balance from Flotation Tests

A grab sample of pyrite flotation feed, i.e. the second tailings stream 41, and pyrite flotation cell tails, i.e. the third tailings stream 45, was subjected to Acid/Base Accounting (ABA) testing. A summary of results is shown in Table 5.

Table 5: ABA Tests on Pyrite Flotation Feed and Tails

AP & NP uriils tons calcium carbonate equivalent per 1,000 tons of solids.

The ABA results indicate a reduction in pyrite reporting to the tails (lower AP), i.e. the second and third tailings streams, 41, 45. A negative NNP (net neutralisation potential) indicates that the pyrite flotation cell feed, i.e. the second tailings stream 41, is a net acid generator and the greater than 1 ratio (6.42) for the pyrite flotation cell tails, i.e. the third tailings stream 45, indicates that the inert stream (i.e. flotation tails) can he used as ground cover/fill material.

It is evident from the above that tire flotation circuit shown in Figure 3 is an effective circuit for producing a pyrite concentrate stream, i.e. pyrite containing slurry that can be used for example in the heap leaching operation described above in relation to Figure 1. Many modifications may he made to the flow sheet of Figure 1 without departing from the spirit and scope of the invention.

By way of example, whilst the embodiment includes steps 1-3 to process waste rock to form the copper sulfide-containing material that is one feed for the agglomeration step 4, the invention is not confined to this combination of steps. By way of further example, whilst the embodiment includes processing a slurry containing pyrite from a mine tailings and removing pyrite therefrom, the invention is not limited to this option and extends to the use of any suitable source of pyrite. For example, the invention extends to adding pyrite-containing tailings directly in agglomeration if they contain sufficient pyrite so that a pyrite removal step is not necessary, is an efficient use of these tailings.