Sulfide Ore Treatment Gold – Silver – Copper – Cobalt – Zinc Recovery

A procedure was developed for recovering gold, silver, cobalt, copper, and zinc from a massive sulfide ore by a hydro-metallurgical process. The procedure consists of (1) oxygen pressure leaching; (2) iron, arsenic, and copper removal from the leach solution by precipitation; (3) selective extraction of cobalt and zinc from solution; (4) electro-deposition of the cobalt and zinc from the strip liquor; and (5) cyanidation of the pressure leach residue to recover gold and silver. The results are discussed in terms of efficiency of metal recovery and conclusions drawn as to possible benefits and broad applications of the process.


Ores that contain sulfide minerals are important resources for many of these vital commodities. Sulfide minerals are common forms for the strategic and critical metals cobalt and nickel.

Metallurgical processing of sulfide minerals can be complex because the minerals normally contain several associated metals. Cobalt and nickel ores usually contain copper, which can be present in a variety of forms, or other common metals; the cobalt and nickel are typically minor values. Lead, zinc, and copper are often associated with each other. Also, gold and silver are commonly associated with those base metals. Mineral recovery procedures must therefore deal with several metals

Electronic Ore Sorting Copper Ore

This process uses electronic ore sorting or “pre-concentration” as an added step before normal concentration to develop a processing system for the native copper ores. Successful ore sorting can lead to cost reductions in the following areas:

  1. Materials handling, and hoisting (if sorting is done underground).
  2. Capital and milling operations.
  3. Mill tailings disposal, as well as decreasing the amounts of them produced.

Such reduced costs could open up large reserves of the low-grade and deep native copper deposits still left in Upper Michigan.

The electronic ore-sorting test program consisted of plant-scale sorting and lab sorting. Plant sorting was done to determine the sortability of different native copper ores and the efficiency of the electronic ore sorters. Tests were run at the sorting plant owned by Minerals Recovery Corp. (MRC) in Painesdale, Mich.

Lab tests were performed at Michigan Technological University, Houghton, Mich. They were done to determine the efficiency of a belt sorter equipped with a second sensing coil located above the belt, and to determine the sorting characteristics of larger ore size fractions than those used in the plant

The ore sorting system performs three basic operations-singulation, detection, and ejection. Singulation is the flow of the material that presents each rock fragment to

Copper Electrolytic Refining Process Explained

Experiments on a Porphyry Copper Ore: This research was done partly in the non-ferrous laboratory of the Department of Metallurgy of Columbia University, under the direction of Dr. Edward F. Kern, and completed elsewhere. Acknowledgment is due to Prof. Arthur L. Walker, Dr. Edward F. Kern and Dr. William Campbell of the Department of Metallurgy, for their kind advice and for the inspiration derived from their instruction.

This report is given under the following heads: Petrographic Description (Microscopic Study); Sampling and Preparing Ore for Treatment; Chemical Analysis; Treatment of Ore.


(Minerals are grouped for interpretation purposes and are arranged in each group in approximate order of abundance)


The original character of the rock has been much obscured by modification. The variable texture indicates that the original rock was much brecciated. Silicification seems to have been a prominent feature. Some of the quartz appears to be remnants of primary grains. It must have been primarily an acid intrusive, which, after having been fractured and brecciated, has become still more acid by silicification. There appear to be recorded several sets of movements. The special features of most importance seem to be as follows:

Method of Precipitating Copper

During the last few years we have been doing considerable experimenting on methods of precipitating copper. The first patent on precipitating from sulphate solutions by heating with SO2 under pressure was taken out by us (U. S. Pat. 723,949).

This reaction, CuSO4 + SO2 + 2H2O = Cu + 2H2SO4, is interesting, but there are a number of practical difficulties which will be met with in carrying it out on a scale of any size, the main ones being that it is not easy to get a sufficiently strong solution of SO2 to carry out the reaction, and that the design of an apparatus for heating large amounts of corrosive solutions under pressure is a considerable problem. If these can be overcome, I believe the process may be developed, but I agree with Dr. Ricketts’s opinion that electrolytic methods of precipitation are preferable.

Regarding our work at Douglas, we have felt that to say much about it was a little premature, as experiments are still in progress, but some notes on the preliminary experiments may be of some interest.

The general method which we adapted for the tests was sulphatizing roasting, leaching, and electrolysis from sulphate solutions, using depolarization.

The reason for the consideration

Leaching Copper: Iron form Electrolyte

The solvent we would use; how we would precipitate the copper from the solution, and what we would do with the iron in the electrolyte. Without going into the details of the reasons, we decided that sulphuric acid would be the most satisfactory solvent and that we would recover the copper from the solutions by electro-deposition. As to how we would take care of the iron in the electrolyte, we had to choose between controlling the iron (i.e., keeping it in the ferrous state) in the solution, and eliminating it from the solution. The removal of the iron appeared to offer the more attractive field.

Briefly, the method followed involves leaching with sulphuric acid, removing a portion of the iron from the solution, and precipitating the copper electrolytically,

Regarding the leaching per se, I do not think I could say anything which would be of any particular interest. There are certain factors which govern the extraction of copper from an ore, and when these factors are given due consideration, I think we can get about the same extraction with one process as with another.

In considering how to remove iron from the electrolyte, we were reminded of the work which had been done

How to Recover Copper from Solution

At the beginning of our investigation we seriously considered what I called the “brutal method” of leaching, namely, the manufacture of sulphuric acid, the solution of the copper from the ore with such acid, and the precipitation of the copper by metallic iron, with the resultant complete, or nearly complete, destruction of both acid and iron and the production of an impure cement copper that will have to go through the process of smelting and refining. The results of Mr. Croasdale’s tests and Mr. Wedge’s cost figures indicated that such a course was commercial, and we concluded that the 1½ per cent. Ajo ore, with no overburden, mined by steam shovel and crushed coarse, would yield a profit on a 12c. copper market if a cheap grade of Alabama pig iron were used.

But it occurred to me, as it had occurred to many engineers, that oxide of iron could be reduced to metallic iron without fusion, and if so we might bring Bisbee sulphide s to the mine, calcine them for the manufacture of sulphuric acid and then metallize the available iron in the impure calcine, already containing values requiring recovery, and use this for a precipitant. I found at

Overpoling Electrolytic Copper

The current meaning of the term, copper overpoled in the reverberatory furnace, is that poling has been carried beyond the tough-pitch stage, with the result that the reduction has been carried too far, causing the copper to become porous and brittle, and thus unfit for industrial purposes. It will be shown that the brittleness of furnace-overpoled electrolytic copper must generally be attributed to other causes than over-reduction. The present investigation, dealing with such pure metal as electrolytic copper, excluded the consideration of the effects that elements like arsenic, antimony, lead, bismuth, nickel, etc., might have if present in the oxidized or the metallic state; it confined itself to the remaining active agents, cuprous oxide, gases and temperatures, and incidentally to sulphur and iron. The plan of work was to examine samples of tough-pitch and furnace-overpoled copper from the same charges as obtained from works, to eliminate all the oxygen from the tough-pitch copper by reduction in a crucible, and to compare the results.

(a) Samples.—In addition to the samples from the two refining-charges (Nos. VIII. and IX., Table IX.) discussed in the first part of this paper, there were examined five specimens of electrolytic copper from Eastern works (samples Nos. I.,

Assaying Gold & Silver from Copper Alloys

The so-called “combination method” is generally used in assaying bar copper for silver. It has been modified from time to time. Briefly outlined as now practiced, it is as follows:

One A. T. of the borings is dissolved in dilute nitric acid. When solution is complete the liquid is boiled and then filtered to remove gold. The filtrate is treated with sufficient salt solution to precipitate all the silver, but avoiding any unnecessary excess. The liquid is allowed to stand overnight and next morning the silver chloride is collected on a fresh filter, which, together with the paper containing the gold and insoluble matter, is scorified and cupelled. Formerly many assayers added sulphuric acid to the nitric acid solution of the copper and silver and then acetate of lead, thus producing a heavy precipitate of sulphate of lead which was supposed to entangle the silver chloride and prevent it from passing through the filter. As a matter of fact the use of sulphuric acid and lead salts is entirely unnecessary. Very few assayers now make use of them. If it is not possible to let the silver chloride settle over night, accurate results may be obtained by stirring the liquid vigorously

Refining Electrolytic Copper

The object of refining copper in the reverberatory furnace is to obtain a metal which will have the highest attainable degree of malleability, ductility and electric conductivity, and present at the same time a level surface when it solidifies in the mold after casting. These desirable physical properties are governed by the character of the impurities and the forms in which they are present, by the amount of cuprous oxide retained by the copper, by the quantity of gas held in solid solution, by the casting-temperature, and by the thickness of the casting. The effects of impurities, of cuprous oxide and of gases upon the mechanical properties of copper have been studied by Hampe in his classical paper “ Contributions to the Metallurgy of Copper.” The most recent research into the effect of metals upon the electrical conductivity of copper is that of Addicks. The influence of cuprous oxide upon the electrical conductivity has been investigated by Walker and Addicks. The absorption of gases has received attention by Hampe, Stahl and Heyn. The effects of casting-temperature have been noted by Stahl.

The present paper contains the results of two lines of investigations embodying:

  1. a study of the physical and

Copper Refining: Explained Step-by-Step

In refining copper, the metal is melted down in a reverberatory furnace in a more or less oxidizing atmosphere and then further subjected to an oxidizing smelting in order to eliminate the common impurities, most of which have a stronger affinity for oxygen than has copper. In these operations some of the copper is oxidized to cuprous oxide and dissolved by the metal bath. When the quantity of dissolved cuprous oxide has reached about 6 per cent, the metal is said to have been brought to “ set-copper.” A button-sample will show a depressed surface and, when broken, a single bubble at the apex of the depression; the fracture will be brick-red and dull. It is essential to carry the oxidation to this point in order to know that the impurities have been oxidized as far as it is possible under the given working-conditions. Nearly all the cuprous oxide of the set-copper is now reduced to the metallic state by poling, when “ tough-pitch ” copper will be obtained. A button-sample will show a flat surface. Upon breaking, it will be found that the former bubble has disappeared and that the fracture has become rose-colored and shows a

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