Museum Bulletin Volume 141-144

Museum Bulletin Volume 141-144

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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. 1910 edition. Excerpt: ...thf marketable products. b Includes crude and calcined gypsum, but not manufactured plaster of paris. COMPOSITION AND CHARACTERS OF GYPSUM Chemical and mineralogic characters. Gypsum is a hydrated calcium sulfate with the formula CaS04. 2H20. Its ideal composition is represented by the following percentages by weight: lime (CaO) 32.5; sulfuric acid anhydrid-(SO., ) 46.6; water (H..O) 20.9. The crystallized variety of gypsum may show a close approach to these percentages, but the ordinary rock and earthy gypsum employed in the industries contains a variable proportion of foreign matter which amounts generally to several per cent of the whole mass. The crystals of gypsum belong to the monoclinic system and are usually formed by a simple combination of faces. According to the relative development of the latter, they may be tabular or flattened, prismatic. Or elongated into acicular individuals. They are sometimes twinned so as to yield arrowhead forms. The common types of crystals are represented by the accompanying figures. The F.G. 1 Cryit ils of gypsum. At the right a twinned for n. (H. P. Whitlock, del.) crystals are characterized by an easy cleavage parallel to the principal plane (face b in figures). Thin Hakes so produced are flexible, but not elastic like mica to which they bear some resemblance. If bent sharply they break in a diagonal direction with the production of fibers. The cleavage plates of gypsum can be distinguished from foliated talc by their greater hardness, which is inferior, however, to that of anhydrite or calcite. Gypsum occupies the second place in the Mobs scale of hardness, according to which certain minerals are selected as standard and numbered in order of increasing hardness from 1 to 10. In this scale talc is..show more

Product details

  • Paperback
  • 189 x 246 x 10mm | 331g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236957989
  • 9781236957986