Geology of the Pegmatites and Associated Rocks of Maine; Including Feldspar, Quartz, Mica and Gem Deposits

Geology of the Pegmatites and Associated Rocks of Maine; Including Feldspar, Quartz, Mica and Gem Deposits

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...feet across. The bare ledge to the north of the smaller pit for a length of 40 or 50 feet and a width of about 30 feet shows feldspar in crystals 2 to 4 feet across but containing numerous small crystals of black tourmaline. In the larger pit there is a small amount of feldspar of commercial grade at its northwest end, but in the smaller pit and in the unopened ledge near the pits black tourmaline is so intimately and abundantly associated with the feldspar as to render most of the latter valueless for pottery purposes under present commercial conditions. The coarsest and most highly feldspathic portion of the deposit as exposed in the larger pit contains some clevelandite and granular lepidolite and a few colored tourmalines of pink and green tints, which are translucent to opaque. A few small pockets occur and several less than a foot in diameter were exposed at the time of the writer's visit. In some of the pockets a few transparent tourmalines of gem quality were found during the mining operations. South of the workings the ledge shows very little feldspar of pottery grade and within 200 feet there begins to be some admixture of schist with the pegmatite. Muscovite has been saved during the mining, but most of. it is what is known as wedge mica and would be valueless except as a source of ground mica. Biotite or black mica is very rare, black tourmaline being the principal iron-bearing impurity. The trend and exact limits of this deposit could not be determined, but there is every indication that the supply of feldspar suitable for use in the pottery trade is very small, most of the material showing too great an abundance of black tourmaline. An examination of the whole coast of the hill south of the pits showed no spar or other...
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Product details

  • Paperback
  • 189 x 246 x 4mm | 136g
  • Miami Fl, United States
  • English
  • Illustrations, black and white
  • 1236571290
  • 9781236571298