Bulletin Volume 5-7

Bulletin Volume 5-7

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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. 1902 edition. Excerpt: ...Owing to the approximate uniformity of the higher shales and thin sandstones, plate 12, together with their many structural disturbances it l1as been difficult in many places to accurately locate the horizon of such ore bodies as occur within them. In the past it has been customary to refer to such deposits in a general way as "upper contact" ores. The proximity of some of these ore bodies to a heavy bed of scolithus sandstone known as the "worm-eaten" sandstone near the upper part of the Cambrian has possibly given origin to the name. Careful observation has revealed the fact that valuable ore bodies may be found at several horizons between the basal quartzite and the scolithus sandstone, hence the distinctive meaning of the term "upper contact" has largely disappeared. The lower contact ores are in many places underlain A Contribution to the Geology of the Northern Black Hills. Annals N. Y. Acad. Sci. 1899, Vol. XII. No. 9, p. 229. by quartzite sufficiently auriferous to be classed as ore. This is particularly true of the North Lead, Yellow Creek and Ruby Basin areas and may upon further examination be found common in other localities. So far as known all ore bodies worked in the Ruby Basin, Yellow Creek, Crown Hill, North Lead and SheeptaiL Gulch localities are on or within the lower quartzite. On Squaw creek higher ores are worked, and in some places the definite horizon can be readily learned. At the Cleopatra the ore bodies are immediately beneath the scolithus sandstone, and this is stratigraphically about three hundred feet above the lower quartzite. Whether or not the lower ores are present has not yet been determined, but it is believed that exploratory work will reveal them In the Portland or Green...show more

Product details

  • Paperback | 76 pages
  • 189 x 246 x 4mm | 154g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236551753
  • 9781236551757