Mines and Mineral Resources of Plumas County (Google eBook)

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California State Printing Office, 1920 - Mines and mineral resources - 188 pages
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Page 64 - Williams Group. To the west of Flournoys, about one half mile, is a mountain which is covered by mining locations held by JD Williams. On this mountain the whole outcrop appears to be heavily mineralized by iron and copper in the form of oxides, carbonates, and sulphides. So little development work has been performed that no estimate of the worth of the claims can at the present time be made. It is doubtless the outcrop of an immense mineralized dike. In Cook's Canyon, south of Moonlight Creek,...
Page 52 - Genesee belt. The deposits throughout the Crescent belt are in more or less well-defined quartz veins, running generally parallel to the course of the belt, but in a few cases there are small veins at nearly right angles to the others. The ore is auriferous pyrite, sometimes in small bodies, but generally disseminated in the narrow strip of sheared rock of the partially formed vein, in which there is usually some quartz. The pyrite is nearly always changed to limonite, setting the gold free and staining...
Page 18 - ... The Cosmopolitan mine is on the contact of the granodiorite with the Hosselkus limestone and Swearinger slate. The ore is bornite and chalcopyrite, forming solid bodies up to 15 feet in thickness, with greater dimensions in the plane of contact, along which other smaller bodies of the same ore occur. On the surface the contact is marked by masses of garnet and epidote which were not seen beneath, but in the Duncan mine the garnet and epidote are associated with the ore. The Bluebell mine is in...
Page 13 - The upper courses of the streams are in broad, shallow valleys, but as they approach the middle portion of the block they cut deeper and deeper until they flow in canyons.
Page 8 - Crescent belt occurs in the Premium mine. It is vertical, about 2 feet in thickness, and cuts granodiorite. In the Green Mountain mine one subordinate vein carries a small amount of chalcopyrite, but in general copper is absent in the belt, except at the...
Page 18 - ... on either side. No characteristic contact minerals were observed to suggest that ores in this case were originally contact deposits modified after the development of the slaty cleavage. The Five Bear mine, in the...
Page 30 - Here the exposed channel is 500' wide, with steeply rising rims. On the southwest side the amphibolite rim rises several hundred feet probably without being influenced by faulting.
Page 36 - ... Superior mine, in which the gangue of the bornite is a green fibrous mineral like actinolite. A number of parallel vertical veins of this mineral are well exposed in the open cut and contain disseminated particles and nodules of bornite. The larger ore bodies are free from gangue The wall rock, which is fine-grained granodiorite, is the same on both sides and the veins are sharply defined.
Page 33 - ... escarpment is long and gentle, and Diller referred to it as the plateau slope, which grades into a series of valleys that lie in a northwest-southeast belt. The average elevation of the plateau slope is about 6,000 feet, rising locally to 7,000 feet. Diller points out that the upper courses of the streams are in broad shallow valleys, but as they approach the middle portion of the block, they flow in deep canyons. 4 Op. cit., pp. 9 and 10. Lights Canyon in the Engelmine area is an example of...
Page 16 - The Foreman formation is a succession of shale, sandstone, and conglomerate in which the sediment is for the most part derived from rocks which are not clearly volcanic. The shales are often slaty and locally. have "pencil structure...

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