Contributions to Mineralogy and Petrography; From the Laboratories of the Sheffield Scientific School of Yale University

Contributions to Mineralogy and Petrography; From the Laboratories of the Sheffield Scientific School of Yale University

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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. 1901 edition. Excerpt: ...also cited by him as giving the smallest value of 2E (71 32') must be the richest in water or hydroxyl and poorest in fluorine of any topaz that has thus far been examined. The indices of refraction also show a progressive change along with the variations of 2E as may be seen by the following determinations, given for yellow light by different investigators. As hydroxy! replaces fluorine, therefore, the indices of refraction increase and the strength of the double refraction decreases, as shown by the values 7--a in the extremes: Thomas Range, Utah y--a = 0.0104 Minas Geraes, Brazil y--a = 0.00811 The crystallographic axes are also affected by the isomorphous replacement of fluorine by hydroxyl. The variation however is not very great and only exact determinations can be used for showing it. Mr. C. A. Ingersoll has kindly made for us some careful measurements on a crystal from the Thomas Range, Utah, which, next to the topaz from Zacatecas, contains the least water of any examined by us, and upon which the forms 0 (221) and/, (021) were well developed and gave beautiful reflections. Also on one from Brazil upon which very exact measurements could be obtained from the / (021) faces only, the other forms, the striated prism and the pyramid u, (111) not being suitable for measurement. Utah. Measured. Measured. Calculated. /a/, 021 A 021 = 87 19/ Oao, 221 A 221 = 105 10' 105 W o A 0, 221 A 221 = 49 36' 0 A O, 221 A 521 = 127 47' 127 51' Brazil. Measured. /a/, 021 A 021 = 86 55' The axial ratios are given in the following table and with them a number of others given by investigators who regard them as very exact. a: b: e Utah, Ingersoll 0.528110: 1: 0.477115 Urals, Koksharov 0.528542: 1: 0.476976 Schneckenstein, Laspeyres t 0.531548: 1: 0.475973...show more

Product details

  • Paperback | 136 pages
  • 189 x 246 x 7mm | 254g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236575768
  • 9781236575760