Rosiwal scale

The Rosiwal scale is a hardness scale in mineralogy, with its name given in memory of the Austrian geologist August Karl Rosiwal. The Rosiwal scale attempts to give more quantitative values of scratch hardness, unlike the Mohs scale which is a qualitative measurement with relative values.

The Rosiwal method (also called the Delesse-Rosiwal method[1]) is a method of petrographic analysis and is performed by scratching a polished surface under a known load using a scratch-tip with a known geometry. The hardness is calculated by finding the volume of removed material, but this measurement can be difficult and must sample a large enough number of grain in order to have statistical significance.[2]

Rosiwal scale values
MohsMineralRosiwal hardness
1Talc0.03
2Gypsum1.25
3Calcite4.5
4Fluorite5
5Apatite5.5
6Feldspar37
7Quartz120
8Topaz175
9Corundum1,000
10Diamond140,000

Measures the scratch hardness of a mineral expressed on a quantitative scale. These measurements must be performed in a laboratory, since the surfaces must be flat and smooth. The base value of the Rosiwal scale is defined as corundum set to 1000 (unitless).

See also

References
  1. Williams Postel, A.; Lufkin, H. M. (May 1942). "Additional Data on the Delesse-Rosiwal Method" (PDF). The American Mineralogist. 27 (5): 335–343.
  2. Larsen, Esper S.; Miller, Franklin S. (April 1935). "The Rosiwal Method and the Modal Determination of Rocks" (PDF). The American Mineralogist. 20 (4): 260–273.

Bibliography
  • The Great Encyclopedia of minerals 451 photographs, 520 pages 20'5 x 29'2 cm. Original: Artia, Prague 1986 Catalan version: Editorial Susaeta SA 1989, ISBN 978-84-30515-85-1 (printed in Czechoslovakia)
  • Accurate mineralogy. De Lapparent, A .: 1965 Paris
  • Minerals and study how to Them. Dana L. Hurlbut, S .: New York 1949
  • Schöne und seltene Mineral. Hofmann and F. Karpinski, J .: 1980 Leipzig
  • CORDUANT, William S. "The Hardness of Minerals and Rocks". Lapidary Digest c. 1990.
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