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300-foot level abundant adularia altered analyses angle area mapped argentite augite basalt biotite Brougher dacite Brougher Mountain Butler Mountain calcite carbonate chalcopyrite chiefly chlorite contains cross section crystals decomposed deposits depth Desert Queen dikes displacement district earlier andesite east encountered erosion eruption evidence feldspar formation formed Fraction dacite breccia fracture zone fragments gangue Geol geologic glassy Tonopah rhyolite-dacite Gold Hill Golden Mountain groundmass horizontal hornblende indicate intrusive irregular later andesite lava magma main vein microscope minerals Mizpah Hill Mizpah vein Montana Tonopah Montana vein Mount Oddie nearly northeast occur original orthoclase outcrop oxidized parallel phenocrysts polybasite portion probably pseudomorphs pyrargyrite pyrite quartz quartz veins region rhyolite rock scarp secondary sericite showing shown side siderite Siebert Mountain Siebert tuffs silica silicified Silver Top similar south drift southwest specimen Stone Cabin strike sulphide surface Tertiary Tonopah Extension Tonopah shaft Valley View vein vertical volcanic waters writer
Seite 295 - ... Monographs, (3) Professional Papers, (4) Bulletins, (5) Mineral Resources, (6) Water-Supply and Irrigation Papers, (7) Topographic Atlas of United States — folios and separate sheets thereof, (8) Geologic Atlas of the United States— folios thereof.
Seite 257 - ... the term solfatara is no longer applicable. We have in the elements evolved during the first two periods all the conditions required for filling the Comstock fissure with such substances as those of which the vein is composed. Steam, ascending with vapors of fluosilicic acid created in its upper parts (by the diminution of pressure and temperature, according to well-known chemical agencies) silica and silicofluohydric acid, the former in solid form, the latter as a volatile gas which acts most...
Seite 299 - SLIPS. [Mount each slip upon a separate card, placing the subject at the top of the second slip. The name of the series should not be repeated on the series card, but the additional numbers should be added, as received, to the first entry.] Bain, H[arry] Foster, 1872.
Seite 259 - The steam of the volcano cannot be derived from vadous infiltration, for if it is, whence the carbonic acid ? Both must come from the deeper regions of the Earth ; they are the outward sign of the process of giving off gases which began when the Earth first solidified, and which to-day, although restricted to certain points and lines, has not yet come to a final end.
Seite 91 - Antimonial sulphides of silver, polybasite, very likely stephanite, and smaller amounts of galena, blende, pyrite, and chalcopyrite are also indicated. Of very great interest is the presence of a considerable amount of selenium, which occurs, in part at least, as a silver selenide, and the absence of its usually closely associated element tellurium. The chemical form of the gold is yet uncertain. It is fair to assume that the oxidized ore in its primary sulphide state may have had a composition somewhere...
Seite 257 - The chloride of silicon in combination with steam forms silica and chlorhydric acid. Fluorine and chlorine are the most powerful volatilizers known, and form volatile combinations with almost every substance. Besides silicon, the metals have a great affinity with them. All those which occur in the COMSTOCK vein could ascend in a gaseous state in combination with one or the other of them. They must then be precipitated in" the upper parts as metallic oxides or chlorides, and in the native state.
Seite 297 - B 159. The geology of eastern Berkshire County, Massachusetts, by BK Emerson. 1899. 139 pp.. 9 pis. B 165. Contributions to the geology of Maine, by H. 8. Williams and HE Gregory. 1900.
Seite 94 - The evidence therefore favors the view that these secondary sulphides in the oxidized zone originated from descending surface waters, and probably part, but not all, of the sulphides in druses in the sulphide ore have a similar origin." The waters which descend through the oxidized zone carry sulphates and chlorides, and "wad...
Seite 259 - ... no question of porous or fragmental rocks, and therefore no question of infiltration of vadous water. Turning now to the gases accompanying the eruptions. After steam, chlorine and gases containing sulphur, are the most important, and carbonic acid gas comes next. Their occurrence follows a definite law. So far as it has been possible to approach them, all fumaroles actually within vents contain steam ; but the hottest fumaroles (over 500° C.) on the surface of cooling lava-streams, where approach...
Seite 272 - Basin, southward into the Mojave Desert, together with a portion at least of the Sierra Nevada, constitutes a petrographic province ; that is to say, it is underlain by a single body of molten magma, which has supplied, at different periods, lavas of similar composition to all the different parts of the overlying surface. The limits of this subcrustal basin, however, are not yet defined in any direction.