Field Testing for Gold and Silver - A Practical Manual for Prospectors and Miners



INTRODUCTORY TO TESTING GOLD ORE IN THE FIELD. Occurrence of Gold Ores.-- Free gold, which can be extracted by mercury 2. Gold in association with other minerals. In field tests, gold ores can therefore be tested by amalgamation or by smelting, as hereinafter explained. Free - Milling and Refractory Gold Ores. - The first class includes IS placer gold and free-milling gold ores. Free gold Caries in its condition, and sometimes, fortunately rarely, it appears to exist in an allotropic condition, which will not amalgamate. Much interesting information about gold is found in a Handbook on Gold Milling, by Henry Louis, Assoc. R.S. M,, published by Macmillan Sr Co. That is, the short ton now very generally used in America and South Africa. For treatment on commercial scale see Appendix A p. 135. A 2 PIELQ TESTING FOR GOLD AND SILVER. The second class includes gold locked up in sulphides and tellurides of gold and silver, such as sylvanite and petzite. The cost of treatment of a gold ore depends largely upon the condition of the gold in the ore, whether it is free-milling or the contrary, known as refractory. The free-milling can be extracted more cheaply than the refractory, therefore an ore may be worked with profit when in the first condition which would not be possible in the second. For this reason field tests of gold ores, which will deternine the character of the ore, are of value to the prospector, or indeed to the mining engineer. The latter might very frequently supplement an ordinary assay result with the procedure hereinafter given under the head of Pan-Amalgamation Assay. A field test may indicate that gold is present, and, ss generally performed, some idea may be obtained as to whether it is present in a large or in a small quantity. fanning.--The usual test of free-milling gold ore or auriferous gravel is panning. The procedure with gold quartz is to pound it up in an iron mortar with a pestle, and pan it down in a gold pan . It will be found advantageous to keep only a small quantity in the mortar at a time. Pulp.-The pounded ore, or pulp, should be put tllrough a sieve into a pan. Pan...

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