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Proprietors Mining and Scientific Press, 1896 - Assaying

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Page 30 - The true weight is the square root of the product of the apparent weights, but if their difference is small, the error is inappreciable.
Page 104 - ... knead with a like quantity of salt and candle grease or any other fat, and cast into the fire, when the characteristic colors — first blue, then green — will appear. This test is better made at night. GALENA. — Black zinc blende is often mistaken for galena. The two may be distinguished by the infallible sign: The powder of galena is black; that of blende, brown or yellow.
Page 103 - ... (.5) of a grain, then the value of the gravel would be — • gold being 780 fine — $0.84 per cubic yard. SIMPLE ORE TESTS The following simple tests will show whether an ore carries any precious metals. Afterwards samples of the rock should be assayed to ascertain the amount of value per ton. GOLD. — Powder; roast if sulphurets are present; grind very fine and wash in pan or spoon; examine with lens; yellow particles not soluble in nitric acid. The color of pure gold is bright yellow, tinged...
Page 45 - ... processes, but each is better, suited to certain classes. Mr. Aaron argues that while an assay by the litharge process " is quickly made, and generally gives accurate results," yet " it has the disadvantage of requiring considerable modification for the various ores, as to the fluxes proper, and to the reducers or oxidizers by which the production of lead is controlled. Sometimes a preliminary assay is necessary.
Page 51 - For ordinary ores, containing little or no sulphuret, some quartz, clay, lime, iron oxide, etc., this formula will in general suffice: — Ore 1 part\ Litharge 3 _.
Page 98 - The specific gravity of the gold and of the quartz is generally assumed, the former at from 17 to 19, the latter at 2.6; that of the specimen is found by weighing it in air and in water, and dividing its weight in air by the difference ; in this case the easiest rule to remember is this: — Divide the specific gravity of the gold by that of the quartz and by that of the specimen. From...

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