Rosiwal scale

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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.

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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

Mohs MineralRosiwal hardness
1 Talc 0.03
2 Gypsum 1.25
3 Calcite 4.5
4 Fluorite 5
5 Apatite 5.5
6 Feldspar 37
7 Quartz 100
8 Topaz 175
9 Corundum 1,000
10 Diamond 140,000

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

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August Karl Rosiwal was an Austrian geologist.

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14
HgS
8
. Danielsite is very fine grained and hard to observe in hand samples. It generally has a gray color with very brittle and soft physical characteristics.

Northstarite is an immensely rare lead-tellurite-thiosulfate mineral with an ideal formula of Pb6(Te4+ O3)5(S6+O3S2-). Northstarite was first discovered in 2019 by Charles Adan in the North Star Mine of the Tintic Mining District, Juab County, Utah, USA. Northstarite received its name after this type locality where it was originally discovered, the North Star Mine. Northstarite is the fourth thiosulfate mineral that exists on Earth, and although all thiosulfates have essential lead components, northstarite is the first thiosulfate species containing groups of both thiosulfate and tellurite (Te4+O3).

<span class="mw-page-title-main">Kenyaite</span> Mineral

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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