silver

Silver Fineness Determination

This excellent volumetric method commends itself as a means of estimating the fineness of silver—firstly, owing to the large number of possible impurities which do not affect its accuracy (these impurities include Cu—up to 70%— Au, Pb, Zn, Bi, Cd, Fe, Mn, Sb, and As) ; secondly, the method combines accuracy with speed.

The above impurities are the only ones likely to be present in the B. H. A. S. Pty, Ltd. refined silver, and, with the exception of Cu and Au, the others, if present at all, would be well under 0.1 parts per 1000.

Briefly stated, the method consists in the solution of the refined silver in HNO3, addition of ferric alum (indicator), and titration with an alkaline (either ammonium or potassium) thiocyanate solution until the brown ferric thiocyanate is formed, and gives a definite tint to the solution. The method is used at the Port Pirie smelters, and the outstanding feature in the method as there applied is the type of burette employed. This burette enables the operator to read 0.01 of a cc. with ease, whereas, with the ordinary burette fitted with a float, 0.05 of a cc., when a number of readings have to be taken, becomes ….Read more

De-Silverizing Bullion

The de-silverizing of base bullion is carried out in accordance with the principles of the well-known Parkes process.

The base bullion produced by the blast furnace department carries (apart from silver values) impurities, the chief of which are copper, antimony, and arsenic.

In order to more clearly indicate the grade of the base bullion, the following analysis, representative of a half-year’s production of base bullion, is submitted:De Silverizing Bullion

Ag………………………………………………..68.6 oz.
Au………………………………………………0.096 oz.
Cu………………………………………………….0.86%
Sb………………………………………………….0.67%
As………………………………………………….0.32%

Before proceeding with the actual operation of de-silverizing, it is necessary that the impurities, copper, antimony, and arsenic, should be eliminated. This is accomplished in the following steps :

Removal of Copper from Bullion

Copper is largely present in the base bullion as dissolved sulphide, and this is removed by liquation in a reverberatory type furnace, of which the following are the essential details:

Hearth area…………………………………220 sq. ft.
Grate area……………………………………..31 sq. ft.
Ratio hearth area to grate area……………….7:1.
Capacity…………………………………………57 tons.
Working temperature………………..750° to 850° C.
Coal consumption per 24 hours…………2 tons.

The hearth of the furnace is encased in a steel tank 22 ft. 4 in. long by 13 ft. 4 in. wide by 2 ft. 10 in. deep ; the bottom of the tank is covered by a depth of composition conforming ….Read more

Mechanical Roasting in Silver-Lead Smelting

What Colonel Dwight says regarding the treatment of oxidized ores holds true also of the silver-lead smelting operations in Utah. The ore sought for was such as would, with appropriate fluxes, yield slag, and “lead bullion,” as the lead reduced from the ore and carrying its gold and silver, was called. No matte, and probably little or no speiss, was yielded, and hence there was nothing to roast, either of ore or matte. But, by 1880, when I first took hold in smelting, there was quite a production of matte at the works of the Germania Smelting and Refining Co., Utah, because, by that time, ores containing some pyrite and galena were being smelted. This was due, as at the Grant Works, to the more attractive price paid for the treatment of such ores. The matte, containing about 5 per cent, copper, was accordingly heap-roasted and returned to the blast furnace for the recovery of its contained metals. By this time there had been built a long-bedded, hand-rabbled reverberatory roaster with a hearth of about 40 by 10, ft. in size, and in this matte and ore, crushed at the sampling mill, was treated. When, in 1892, I took control of ….Read more

Effect of Manganese on Silver Leaching

In Mexico and elsewhere there are large bodies of valuable silver ore containing manganese which present great, and hitherto insuperable, obstacles to a satisfactory extraction by cyanide. The proportion of the silver that is soluble in cyanide varies greatly and may be as low as 5% only. The mere presence of manganese in the ore is not invariably accompanied by refractoriness of the silver because the writer has known of an instance where ores of apparently similar composition and character and coming from adjacent mines behaved quite differently, one yielding only 50% of its silver and the other 90% under the same conditions. As a general rule, however, when oxides of manganese are present in a silver ore trouble may confidently be expected.manganese

The manganese usually occurs as the dioxide but in what way, if at all, it is associated with the silver has never been determined. There are three possible theories on the subject. The first is that the refractory silver occurs as a silver-manganese mineral. Although no such mineral is described in the text books, there are certain facts which would seem to point to its existence:

(a) The silver is ….Read more

Silver & Cobalt Processing by Gravity and Flotation

The treatment of complex silver cobalt ores occurring with antimony and arsenic require special metallurgical processing to produce concentrates most advantageous for smelting. Gravity concentration is used to initially recover a high percentage of the native silver and cobalt. The concentrate is marketed and payment received for these constituents. Flotation treatment of the gravity tailing recovers additional silver values for marketing at a separate smelter.

The Silver Cobalt Extraction Flowsheet

In this study, the silver occurs essentially as impure native silver together with argentite, cobaltite and other complex sulfides. The flowsheet is based on a 400 ton per day concentrator with special emphasis on “recover your mineral as soon as free.”Gravity and Flotation of Silver-Cobalt

CRUSHING Silver Cobalt Ore

The conventional two stage crushing plant has a rated capacity in excess of 200 tons per 8 hours.
The grizzly undersize (2½”) is combined with the jaw crusher product and conveyed to a double-deck Vibrating Screen. The top deck scalps off the coarse fraction and protects the plus near mesh. All screen undersize is conveyed to the fine ore bin. The secondary crusher product discharges to the common conveyor handling the grizzly undersize and the primary jaw product.

Silver Cobalt ….Read more

How to Process Copper Lead Zinc Ore with Gold and Silver by Flotation

The flowsheet in this study was designed to treat 500 tons per day of a complex base metal ore containing gold and silver values. The presence of free gold offers opportunity to recover these values in the grinding circuit so that the gold could be amalgamated, and marketed directly to the mint. The ore as mined is very wet and sticky and presents certain handling problems.

The Lead Zinc Copper Flotation and Separation Circuit

Lead-Zinc-Copper-Gold and Silver Flowsheet

Every effort is made to recover the minerals as soon as free. Over-grinding causes slime losses which are both unnecessary and costly. The flowsheet is designed for a compact mill of a size that provides economical treatment at this tonnage.

Crushing Plant

The wet ore is delivered to the coarse ore bin directly from the mine and dumped through a grizzly to prevent any large rocks from lodging in the bin and causing subsequent problems in feeding the crusher. The stored coarse ore is crushed in two stages to produce a ¾-inch product. The reciprocating feeder, overhead eccentric-type jaw crusher, and oversize vibrating screen were selected to alleviate problems in handling a wet and sticky ore. All chutes and transfer points ….Read more

Silver Lead Zinc Ore Processing Method using Flotation

Sulphide ore of lead and zinc containing considerable silver was submitted for testing with the purpose of determining a flowsheet for the production of separate lead and zinc concentrates for marketing at their respective smelters. It is necessary to recover as much silver as possible in the lead concentrate as a higher return for this silver is realized than for the silver in the zinc concentrate. The ore contained sphalerite, a portion of which was easily floatable but difficult to depress in the lead flotation circuit.

Also, the recovery of silver minerals occurring in a lead, zinc sulfide ore is efficiently accomplished using Flowsheet #2. The process consists of selective flotation to produce a mixed silver, lead concentrate for maximum smelter return and a separate zinc concentrate. Over-grinding of silver minerals is detrimental to efficient flotation recovery, so the Flash Flotation Unit-Cell is used in the grinding circuit to recover a large part of the silver and lead values as soon as liberated. The flowsheet is for a plant having a capacity in the range of 300 to 500-tons per day.

A Pb-Ag-Zn Separation Circuit Flowsheet #1Flowsheet for Lead-Silver, Zinc Ore

Crushing Section

The crushing ….Read more

Gold and Silver Leaching by Cyanidation

Introduction to Gold and Silver Leaching

The cyanide leaching process is the most important method ever developed for extracting gold from its ores. The early development of the process is attributed to a Scotchman, John Stewart Mac Arthur, in collaboration with the Forrest brothers. The method was introduced into South Africa in 1890. From there it spread to Australia, Mexico and the United States. Now it is used in practically all the major gold mining camps of the world.

The reasons for its widespread acceptance are economic as well as metallurgical. It usually obtains a higher recovery of gold than plate amalgamation and is easier to operate than the chlorine or bromine process. It produces the final product in the form of practically pure metal. Thus the production from a large cyanide mill will be represented by a comparatively small gold bar, which is easy to transport. Accordingly gold mines can be located in relatively inaccessible districts served only by aeroplane or mule train.

However, the gold metallurgist must be familiar with the other processes of gold treatment, such as amalgamation and flotation, as they are frequently used as an auxiliary to the cyanide process.

General Precious Metal Leaching Theory

Before going into the theory ….Read more

Yamana Gold’s Cerro Moro Mine by Numbers [infographic]

Despite the fact that the mining industry is living dark times, especially due to the downfall of gold’s price, the company Yamana Gold is definitely developing its Cerro Moro gold and silver project.

The deposit, located in the southern Argentine province of Santa Cruz, will move forward thanks to an initial investment of $450 million. However, this is not the only interesting number you can find out about Cerro Moro. Check this new infographic brought to you by Mining Examiner.

CerroMoroMine

Meet the world’s 10 biggest silver mines

Curious to know more about the 10 biggest silver mines in the world? Let’s go on a journey based on contained silver reserves through Mexico, the world’s biggest silver producing country, and Poland, among other countries.

1. Penasquito

6168906733_8469db4c78_b Photo: Goldcorp

The world’s biggest silver mine by reserve is located in the north-eastern part of the State of Zacatecas, Mexico, and operated by Goldcorp.

2. Polkowice-Sieroszowice

787px-KGHM_Polska_Miedz_Sieroszowice Photo: Wikimedia

Located in the Legnica-Glogow Copper Belt of Poland, this mine is owned and operated by the state-owned mining enterprise KGHM.

3. San Cristobal

04 Photo: Minera San Cristobal

This silver-lead-zinc mine is located 500 kilometers south of the city of La Paz, in Bolivia, and owned by Minera San Cristobal.

4. Pitarrilla

Photo: Silver Standard Photo: Silver Standard

The fourth biggest silver mine in the world is located in the State of Durango, Mexico. The deposit is owned by the Vancouver-based mining company Silver Standard.

5. Lubin

….Read more

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