Bulletin, Issue 681

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U.S. Government Printing Office, 1918 - Geology
 

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Page 50 - ... in width. This charge should be introduced into the incandescent coals of a blacksmith forge which has been blown until little black smoke is evident. The iron should be sunk into a depression in the glowing coals so that they stand a half inch or so above the sample on all sides. Then the draught should be increased until the iron is heated white hot. Oxidized zinc ore will take fire at this point, burning with a bluish flame and emitting white fumes of zinc oxide. The density of these fumes...
Page 67 - ... that lead has driven iron or zinc out of its sulphide combinations, but lode ores afford surprisingly few examples of pseudomorphous replacements of sphalerite or pyrite. Possibly the strong tendency of galena to assume its own crystal form has obscured its pseudomorphic replacement of other minerals. It has frequently been stated that zinc sulphide has been precipitated at the expense of iron sulphide and that zinc has driven iron out of its sulphide combination, but no examples of the pseudomorphous...
Page 31 - The nicholsonlte is Identical with aragonite in all but three particulars. Those specimens with high percentages of zinc have a higher specific gravity than aragonite, show a decided adamantine rather than a vitreous luster, and have a better cleavage (good pinacoidal and poor prismatic) than pure aragonite. The variety was found in the oxidized iron-manganese ore in the blue limestone and was named after SD Nicholson, of the Western Mining Co., who brought it to the attention of the writer. BARITE....
Page 50 - Probably the quickest method for quickly ascertaining the approximate grade of oxidized zinc ore is to place about a teaspoonful of the finely powdered material to be tested upon a piece of iron or steel barrel-hoop, one and a half to two inches in width. This charge should be introduced into the incandescent coals of a blacksmith forge which has been blown until little black smoke is evident. The iron should be sunk into a depression in the glowing coals so that they stand a half inch or so above...
Page 68 - zinc is not, as a rule, deposited as a secondary sulphide, and no authentic case has been recorded where it replaces pyrite, as chalcocite so often does.
Page 48 - Butler, 1 who analyzed and determined the specific gravity of nearly 50 specimens and found that they all absorbed water slowly, but at varying rates, for many hours.
Page 10 - ... line of transition. The sulphides first encountered are invariably heavy sulphides of zinc, carrying a little iron and very, little lead. They have a close crystalline structure and lie in a laminated form, the lines of fracture being nearly vertical. Upon these cleavage planes, crystals of cerussite are found, and often a small incrustation of native silver. Such deposits, where first encountered in passing from oxidized to unoxidized ores, are always lowest in silver. In their further extension...
Page 10 - ... with the limit and extent of such oxidizing action. As a corollary of the above, it is believed that at the present stage of development in Leadville the sulphide of zinc forms a larger part of the unoxidized ores than will be found in future and deeper exploration.
Page 32 - WF, and Penfield, SL, Some additions to the alunite-jarosite group of minerals: Am.
Page 49 - Geology, vol. 8, pp. 14-15, 1913. air. He states that in consequence of these and many other tests, it can be said that an ore with a specific gravity of less than 3.3 as determined in this way is in all probability of too low grade (under 27...

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