Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . by ferroussulphate or as sulphide by hydrogen sulphide ; in the latter casethe precipitate is pressed, dried, roasted, and finally fused. A more recent method is to submit the finely crushed ore, whichhas previously been roasted, if sulphide or telluride, to a weak so-lution of potassium cyanide. With the aid of the oxygen of theair, or of some oxidizing agent, the potassium cyanide dissolvesthe gold. The solution is then drawn off into large vats wherethe gold is precipitated by means of zinc turnin
Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . by ferroussulphate or as sulphide by hydrogen sulphide ; in the latter casethe precipitate is pressed, dried, roasted, and finally fused. A more recent method is to submit the finely crushed ore, whichhas previously been roasted, if sulphide or telluride, to a weak so-lution of potassium cyanide. With the aid of the oxygen of theair, or of some oxidizing agent, the potassium cyanide dissolvesthe gold. The solution is then drawn off into large vats wherethe gold is precipitated by means of zinc turnings or the gold maybe separated electrolytically. The method has become of thegreatest importance and comparatively poor ores and tailings fromthe amalgamation process are very successfully treated by it. GOLD. Composition.—Au, usually alloyed i^i°- 489- with Ag, and sometimes Cu, Bi, Rh,or Pd. General Description.—A softmalleable metal with color and streakvarying from golden yellow to yellow-ish white according to the silver con-tents. It is found in nuggets, grains, Butte Co., 288 DESCRIPTIVE MINERALOGY. or scales, usually so disseminated as to be apparent only on in distinct isometric crystals, but more frequently in skeletoncrystals or distorted and passing into wire-like, net-like, and den-dritic shapes. Also occurs included in many sulphides, as pyrite,sphalerite, galenite, pyrrhotite, and arsenopyrite. Physical Characters. H., to 3. Sp. gr., to , metallic. Opaque. Streak, like color. Tenacity, malleable. Color, golden yellow to nearly silver white. Before Blowpihe, Etc.—On charcoal fuses to a bright yellowbutton insoluble except in aqua regia. Any silver present will sepa-rate from the solution as a white curd-like precipitate. If the solu-tion is evaporated to a thick syrup and diluted with water andheated with stannous chloride it becomes purple, and a purple pre-cipitate settles. Similar Species.—Chalcopyrite, pyrite, a
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