The Rosiwal scale is a
hardness scale
The Mohs scale of mineral hardness () is a Qualitative property, qualitative ordinal scale, from 1 to 10, characterizing scratch hardness, scratch resistance of various minerals through the ability of harder material to scratch softer material.
...
in
mineralogy
Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the proces ...
, with its name given in memory of the Austrian
geologist
A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althou ...
August Karl Rosiwal. The Rosiwal scale attempts to give more quantitative values of scratch hardness, unlike the
Mohs scale
The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material.
The scale was introduced in 1812 by th ...
which is a qualitative measurement with relative values.
The Rosiwal method (also called the Delesse-Rosiwal method
) is a method of
petrographic
Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The class ...
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
A grain is a small, hard, dry fruit (caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
in order to have statistical significance.
Rosiwal scale values
Measures the scratch hardness of a
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...
expressed on a quantitative scale. These measurements must be performed in a
laboratory
A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physicia ...
, since the surfaces must be flat and smooth. The base value of the Rosiwal scale is defined as
corundum
Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the pres ...
set to 1000 (unitless).
See also
*
Hardness
In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
*
August Karl Rosiwal
*
Friedrich Mohs
Carl Friedrich Christian Mohs (; 29 January 1773 – 29 September 1839) was a German chemist and mineralogist. He was the creator of the Mohs scale of mineral hardness. Mohs also introduced a classification of the crystal forms in crystal syst ...
References
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, (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.
External links
Glossary of technical mining
{{Mineral identification
Materials science
Mineralogy
Hardness tests