Geological Survey Bulletin Volume 1046

Geological Survey Bulletin Volume 1046

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. Excerpt: ...However, veinlets and irregularly shaped masses transverse to the bedding are fairly common. Locally, uraninite-bearing veinlets cut the transition-dike rocks. Few individual veinlets or masses containing uraninite are continuous for much more than 6 inches; ore bodies are composed of a great many of these disconnected veinlets. The uraninite-bearing veinlets are composed mostly of uraninite and nontronite or chlorite in various proportions. Uraninite commonly occurs as discrete grains that average less than 10 microns in diameter and are disseminated in a matrix of nontronite or chlorite and minute grains of feldspar and quartz which may be relics of unaltered host rock. In some specimens, cubes of galena generally less than 10 microns across are abundant among the uraninite grains. These are much more common in transverse veinlets than in uraninite aggregates that follow the bedding. Locally, small blebs of chalcopyrite, pyrrhotite, or marcasite have replaced some of the nontronite or chlorite and partly or completely surround several uraninite grains (fig. 56). The veinlets are for the most part less than one quarter of an inch thick. The wall rock from one quarter of an inch to several inches outward from the uraninite masses is commonly altered to pleochroic green nontronite and chlorite. Chalcopyrite, pyrrhotite, marcasite, and galena may or may not be disseminated in the altered zone. Figure 57 is a diagrammatic sketch of a veinlet in the Hope adit, about 325 feet from the portal. Galena and marcasite are concentrated in the altered zone; the galena is generally closer to the uraninite veinlet. In some places there is very little alteration adjacent to the uraninite-bearing veinlets and masses. Specimens from the Little Joe claims contain uraninite more

Product details

  • Paperback | 94 pages
  • 189 x 246 x 5mm | 181g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236627024
  • 9781236627025