Mineral Processing

Volatilization of Silver Ore: Chloridizing Roasting

The latest revised edition of Mr. C. A. Stetefeldt’s book on the Lixiviation of Silver-Ores, which appeared very recently, contains no mention of the volatilization of silver in chloritization-roasting—an omission which is the more remarkable in view of the fact that in former editions of the work this important subject was noticed. Moreover, Mr. Stetefeldt has discussed it to some extent in his paper on “ The Stetefeldt Furnace,” in which he criticised certain statements made by me before the Colorado Scientific Society, in a paper entitled “ A Review of the Russell Process; ” and Mr. Morse, in his paper on “ The Lixiviation of Silver-Ores by the Russell Process at Aspen, Colorado,” has given statistics showing the loss of silver by volatilization (including the dust loss, which Mr. Morse estimates at not more than 1 per cent.) on more than 30,000 tons of ore roasted, to have been 9.16 per cent. The matter must certainly be deemed important enough to warrant me in returning to it, and offering, with the aid of the figures made public since my first paper, a reply to the criticisms of Mr. Stetefeldt.

The passages of my paper which he deemed to be “ ….Read more

By | January 23rd, 2017|Categories: Precious Metals, Smelting - Melting - Refining|Tags: |Comments Off on Volatilization of Silver Ore: Chloridizing Roasting

Steam Stamp Milling with Amalgamation

The use of steam-stamps in the crushing of ore for the purpose of amalgamation has been very limited, and little has been written on the subject. As the writer has been operating a mill of this kind during the past year, it is possible that he may be able to present a few points in regard to mill-practice in this line which will be of interest.

The mill herein referred to contains two Tremain steam- stamps, a more detailed description of which will be given below. A bond and lease had been taken on a property on Cross mountain, Gunnison county, Colo., and the parties operating wished to prospect it thoroughly and did not wish to ship out the ore, owing to high freight-rates. They looked around to find some mill that would answer the purpose and not be too expensive. The steam-stamp in question was finally decided on, and the writer was employed to erect and operate it.tremain-stamp

The economy of construction was demonstrated at the outset. The stamps were dropping within ten days from the time that the machinery was unloaded on the ground. A large portion of this period was consumed ….Read more

By | January 23rd, 2017|Categories: Crushing & Screening|Tags: , |Comments Off on Steam Stamp Milling with Amalgamation

Silver Assaying & Cupellation

A great deal has been written of late regarding the loss of silver in assaying; very discordant results have been published by different writers, and much uncertainty exists concerning even approximate losses in a careful determination of silver, as represented by a fire-assay.

In the present paper it has been the aim of the writer to determine as accurately as possible the losses sustained by silver, under certain specified conditions, during the process of cupellation. Such losses are well known to be due to absorption by the cupel and volatilization. The conditions, however, which govern these losses are not believed by the writer to be so well understood. The most important of these are:

  1. The effect of variable quantities of silver used.
  2. The temperature of cupellation.
  3. The character and quantity of impurities in the lead button.
  4. The weight of the lead button.
  5. The nature of the cupel.

The following experiments were made for the purpose of demonstrating, as nearly as possible, the total loss of silver in cupellation under the most favorable conditions to be obtained in commercial assaying.

Chemically pure silver and pure lead were taken. The latter was obtained from test-lead, first melted into ….Read more

By | January 23rd, 2017|Categories: Assaying|Tags: |Comments Off on Silver Assaying & Cupellation

Settling Tank Spitzkasten Classifier

In “ Sorting Before Sizing ” (a paper first announced at the Pittsburgh meeting, but delayed in preparation and now presented at the present meeting) it is shown that if slime-tables are to do their best work on slimes below 0.5 mm. or 0.02 inch in diameter, they must be carefully sorted or classified, and fed to a series of tables suitably adjusted to the different slime-sorts. The reason is that the coarser and finer slime-sorts require respectively different adjustments of the tables. Hence, if the two are fed together upon a table which has, as nearly as may be, average adjustments, fine galena, for example, will go into the tails, or coarse quartz into the heads, or both—losses which could have been largely prevented if the slime had been carefully sorted and each sort sent to its own slime-tables.

As indicated in the paper just mentioned, the present tendency in this country is generally to do away with slime-sorting or “ classification,” and simply to take the overflow from the hydraulic classifier and divide it among the tables by means of a distributing-tank. We must therefore look to the old country to see ….Read more

By | January 23rd, 2017|Categories: Classification, Equipment|Tags: |Comments Off on Settling Tank Spitzkasten Classifier

Cementation of Gold by Zinc: Dilute & Foul Cyanide Solutions

Some months since, the attention of the author was directed to certain statements to the effect that the gold-contents of foul or extremely dilute cyanide-solutions could not be effectively precipitated in practice by the usual zinc cementation of gold called the “zinc-method”.

Such statements caused all the greater surprise, because it is well known that this difficulty is not encountered in other well- known districts, as, for example, in New Zealand, where solutions containing less than 0.05 per cent, of KCy are regularly reduced in practice to below 1 grain of gold per ton, while in Mexico and the United States almost equally satisfactory cementations are not uncommon.

As a result of these representations, however, the author visited several plants at work in the Transvaal, and noted that while at some few mines the cementation was really excellent, at others the effluent, after treatment, was much too high in bullion-contents.

An investigation into the causes of these unsatisfactory results disclosed the fact that more attention to the close packing of the zinc-shavings in the extractor-compartments tended to improve the results, even with the most dilute solutions. The function of the zinc being one of surface, it stands to reason that a compartment well ….Read more

By | January 23rd, 2017|Categories: Laboratory Procedures, Leaching, Smelting - Melting - Refining|Tags: |Comments Off on Cementation of Gold by Zinc: Dilute & Foul Cyanide Solutions

Smelter Slags and Mattes Transport

It is obvious that the choice of the method to be employed in the handling of blast-furnace slags and mattes depends upon local facilities and conditions which may indicate as advisable some particular plan. As a result of the variety of such conditions hardly any two smelters use identically the same method, though they be located only a few hundred feet apart. For instance, of the several plants in Leadville, Colorado, each has a more or less distinctive system. The same is true of Salt Lake City and vicinity. In view of this it is evident that the existing diversity of practice cannot be accepted, prima facia, as evidence of the lack of wisdom at any one works, and the following account of the methods pursued at several leading establishments in the West is offered, without purpose of criticism, as likely to furnish for all parties useful material for consideration.

The Boston and Montana Consolidated Copper and Silver Mining Company.—This company has large mines in Butte, Montana, whence the ore is shipped in cars to Great Falls, 170 miles distant, for treatment. Such ore as is suitably high in copper is smelted in blast-furnaces to a copper-matte, carrying from 50 to ….Read more

By | January 23rd, 2017|Categories: Smelting - Melting - Refining|Tags: |Comments Off on Smelter Slags and Mattes Transport

Excentric Jig

The accompanying figures show the arrangement of a two- compartment excentric jig fitted with adjustable and automatic discharges for drawing off the lower product obtained in jigging minerals, ores, coal, etc., which is designed to remove or separate more effectively the materials treated, as they travel over the jig from the receiving- to the discharge-points.

The discharge-box is constructed to extend across the width of the jig at right-angles to the direction of the movement of the material over the jig-sieve, and to intercept at suitable points the path of the material and remove such of the lower product as has become separated, allowing the remaining material to continue on its passage to the next, and so on to the final overflow- or discharge-end.

Thus the discharges are more directly presented to the lower product, for receiving and removing it, than in the case of small discharge-boxes located at the center or side of the bed, or at the middle of the overflow-end; which arrangements require the lower product to follow a circuitous path before arriving at the discharge, thus consuming more time to effect a separation and lessening the capacity of the jig, or else permitting the material to pass beyond ….Read more

By | January 23rd, 2017|Categories: Equipment, Gravity Concentration|Tags: |Comments Off on Excentric Jig

Electrolytic Assay

The analysis of refined copper is a subject of great importance, and has not received the attention it deserves. Copper metallurgists, therefore, will welcome the paper of Mr. Heath with satisfaction. The state of the art of the chemical analysis of copper has been such that consumers, if they could not afford to run any risk, have been obliged to buy copper from the smelter having the best reputation, and a specification for copper to meet certain requirements could not be drawn up by the mere giving of the chemical constituents. Mr. Heath has brought the analysis of the copper to such a state that when a specification calls for copper “ equal to Lake copper ” one will know immediately what percentage of the pure metal to expect.

It seems to be a pretty well established fact that the copper of Lake Superior is practically free from antimony and bismuth ; and, with the exception of arsenic, the other elements are easily separated from copper by electro-deposition in an acid solution. The authorities differ in regard to the question whether antimony is deposited with the copper in an acid solution. Classen recommends the employment of a solution containing 10 per ….Read more

By | January 23rd, 2017|Categories: Assaying, Smelting - Melting - Refining|Tags: |Comments Off on Electrolytic Assay

Assay Determination of Arsenic & Antimony

Determination of Arsenic and Antimony Together: Instead of separating arsenic from antimony in the hydrochloric-tartaric acid solution which was finally obtained, dilute the solution to four times its volume; pass sulphuretted hydrogen to saturation; filter the combined sulphides on a 4 cm. filter (weighed and dried in weigh-bottle at 110° C.); wash with water, absolute alcohol, carbon bisulphide, and finally absolute alcohol again, very carefully; then dry at 110° C., cool and weigh. More about Electrolytic Assay.

By allowing to dried filters in weigh-bottles the same time for cooling in the desiccator when getting weight of bottle and filter-paper only, as afterwards when filtered sulphides are dry and ready for weighing, very uniform results are obtained.

Arsenic being precipitated as As2S3 and antimony as Sb2S5, their respective factors being 0.609 and 0.600, the factor 0.6 is used in calculating, from the weight of the combined sulphides, the percentage of arsenic plus antimony.

Determination of Arsenic as Trisulphide

Re-dissolve the sulphides in a solution containing hydrochloric acid, water and chlorate of potash. Dilute to at least twice the volume. Pass through the warm solution sulphuretted hydrogen to saturation, to insure the thorough reduction of the solution. Arsenic will be precipitated as trisulphide. After 5 ….Read more

By | January 23rd, 2017|Categories: Assaying, Smelting - Melting - Refining|Comments Off on Assay Determination of Arsenic & Antimony

Smelter Water Cooling Apparatus

In the planning and erection of smelting-works, especially of such as contain the modern large water-jacketed blast-furnaces, we are often confronted with an insufficiency in the water-supply. It may be impossible to find in the immediate neighborhood of the selected site a sufficient supply to furnish the jackets with cold water. Or there may be enough water for this purpose, but it may be highly charged with scale-forming minerals held in solution. Or, the main water-supply, if pumped from the workings of a mine, may carry iron or copper-salts, or even some free acid in solution, all of these substances being derivable from the oxidation of sulphuret-ores in the mine. Moreover, such mine-waters sometimes contaminate the waters of the creeks, so that these become unavailable, and we have to fall back on an inadequate supply of pure water furnished by some spring or springs, entirely too small in volume for our needs, unless used over and over again. This last alternative, using the same water repeatedly for the cooling of the water-jackets of a furnace, necessitates, of course, the cooling of the heated water before each new introduction of it into the water-jackets. The effective cooling of the large volumes ….Read more

By | January 22nd, 2017|Categories: Equipment, Smelting - Melting - Refining|Tags: |Comments Off on Smelter Water Cooling Apparatus