Mineralogical Notes

Mineralogical Notes

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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. 1912 edition. Excerpt: ... The large face is taken as the brachypinacoid, and the chief forms noted, as shown in figure 4, are: &(010), m(110), and e(012). In addition to these forms the macropinacoid a(100) is sometimes present as a narrow face. Occasionally the crystals are much longer and the prism faces more developed in comparison with the brachypinacoid. The common habit of the crystals is shown in figure 4. A better idea of the shape of the crystals can be had from figure 3, on page 53, which shows a variscite crystal so drawn as to bring the brachypinacoid &(010) in front. The rectangular tabular shape of the crystals, due to the large development of the brachypinacoid, is well illustrated in the same figure. Several other forms are present on these crystals, but they could not be determined. On crushing some of the coarsely crystallized aggregate and examining it under the microscope one occasionally sees an acutely-terminated crystal which has the corners replaced by small faces, probably those of the unit pyramid. In orienting the crystals of variscite three positions are available, depending on the pinacoid to which the broad face is referred. This broad face is generally slightly striated vertically. In conformity with the analogous mineral scorodite, the striations are taken as parallel to the c axis. Striated crystals of scorodite have been described by several authors. Kokscharow1 states that the form 010 is strongly striated vertically. Zimanyi2 describes scorodite crystals on which the prism d 120 is vertically striated and Lacroix3 mentions vertical striations on 120 and the two pinacoids 100 and 010. The crystals of variscite have been so oriented that the broad face is b 010, as already described and illustrated in figure 3. Lacroix 4 mentions...show more

Product details

  • Paperback | 36 pages
  • 189 x 246 x 2mm | 82g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236519124
  • 9781236519122