Free Milling Gold Ores

Free Milling Gold Ores

Many problems on free milling gold ores have been solved by the 911MPE Testing Laboratory. One free milling gold ore received for testing the application of the Mineral Jig in the Ball Mill Classifier circuit gave the following results:

Head Ore, 0.65 oz. Gold per ton (Assayed)

0.643 oz. Gold per ton (Calculated)

Amalgam from Amalgamation of Jig Concentrate:

0.471 oz. Gold from one ton head ore, or 73.3% of Gold from the original heads.

Residue after Amalgamation:

10.14 oz. Gold per ton of residue, or 16.1% of the Gold from the original heads.

Ratio of Concentration: 98:1 Jig Tailing:

0.07 oz. Gold per ton tailing or 10.6% of the Gold in the heads.

On this ore, the Mineral Jig, with its selective action, recovered 89.4% of the ’gold in the ore, producing at the rate of only one ton of concentrates from every 98 tons of ore. Calculations from these results, based on gold payment at a smelter, and at the mint, deducting a minimum smelter treatment charge per ton of concentrates, shows that the jig concentrates shipped without amalgamation would return per ton of head ore; whereas shipping bullion to the mint and amalgamation residue to a smelter would return $ some per ton of head ore, or a difference of a few $ per ton of ore in favor of amalgamation. At a lower ratio of concentration, tests showed that the recovery could be increased to as high as 94% of the gold in the ore.

Industrial Applications

More and more Industrial operations are turning to reclamation of products formerly considered waste, and manufacture of additional by-products. Test work on such problems is continually going forward.

One company which uses a large amount of silver was reclaiming a considerable portion of this valuable metal from waste product by smelting. Recovery by this method was relatively good but there was a large quantity of slag from the original smelting operation on hand which contained much silver in the form of fine beads.

The 911MPE Ore Testing Laboratory was called upon to attempt a solution to the recovery of this silver. Test work indicated that the material could be crushed, ground and then treated with the Mineral Jig. A high recovery of this silver in a concentrate assaying over 50% silver was found possible.

Similar methods can often be used in recovering valuable metals from old retorts and crucibles. Valuable minerals contained in floor sweepings in industrial plants can often be profitably recovered using standard ore dressing equipment. In their work the engineers in the Ore Testing Division keep constantly before them not only the question of “can the metallurgical results be obtained,” but “can they be obtained in a manner that will make a profitable operation?”

Such work has not been confined to ores from the United States alone but also on samples from all parts of the world; tin from Bolivia, China and the Malay States; gold and copper from Mexico, Africa and South America; silver and manganese from the East Indies; complex ores from Australia and New Zealand; gold and silver ores from Alaska; potash from France and many other ores from Bolivia, Yugoslavia, Canada, South America, Alaska, Central America, Turkey, Mexico, Australia, the East Indies and elsewhere.

More and more the desirability, and the actual necessity, of conducting exhaustive test work on ores and industrial products at the very beginning of such operations is becoming recognized. It is for this purpose and also as a service to the Ore Dressing and other Industries, that the 911MPE Ore Testing Laboratory offers. The charges for this test work are very nominal. Just sufficient to cover the actual operating costs including the analysis and assay (both fire and chemical) of the test products made.

Pilot Plant Testing

Pilot plant testing charges are based on laboratory pilot plant rental, power, water, lights, assays, chemicals, labor, supervision, and any special equipment which may be required. Batch testing should always be performed first in order to establish pilot plant flowsheet requirements, ore treatment characteristics, and reagents necessary to intelligently proceed with the work on a pilot plant basis.

A minimum of 5 tons of ore is necessary for a pilot plant test using the facilities available at the Denver Equipment Company Laboratory. The pilot plant is capable of treating 200 to 300 lbs. of ore per hour and usually a two-week period is required to complete a pilot plant test on 5 tons of ore.

Pilot plant tests are only recommended where it is not possible to determine from batch or cvcle tests the disposition of all products or middlings. Often these tonnage lot tests are necessary to secure several hundred lbs. of concentrates or products for further evaluation in establishing markets, etc. This is particularly true on non-metallics such as talc, clay, phosphate, potash, fluorspar, feldspar, barite, etc.