Mohs Scale


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Mohs scale

[′mōz ‚skāl]
(mineralogy)
An empirical scale consisting of 10 minerals with reference to which the hardness of all other minerals is measured; it includes, from softest (designated 1) to hardest (10): talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum, and diamond.

Mohs’ Scale

 

a ten-point scale for measuring the relative hardness of minerals. Proposed by the German scientist F. Mohs in 1811, the scale (see Table 1) comprises ten standards of hardness.

Table 1. Mohs’ scale of hardness
1Talc6Orthoclase
2Gypsum7Quartz
3Calcite8Topaz
4Fluorite9Corundum
5Apatite10Diamond

The relative hardness is determined by scratching the surface of the test specimen with a standard of the Mohs’ scale. If, for example, the standard apatite, having a hardness of 5, scratches the specimen and the specimen itself leaves a mark on the surface of fluorite, the standard with a hardness of 4, then the hardness of the mineral being tested is approximately 4.5. Mohs’ scale facilitates the rapid identification of minerals.

References in periodicals archive ?
Rock drillability classification based on the Mohs scale [7]
The plastic materials used for mold cleaning fall in a hardness range of 3.0 to 4.0 on the Mohs scale. This bridges the gap between steel grit/shot (very hard) and agricultural products such as walnut shells (very soft).
At first these gems, the color of the sky as evening descends, were thought to be an exceptionally beautiful form of sapphire, but at only 6.5 on the Mohs scale, they were much too soft for that label to stick.
10 Questions 1 What is the Mohs scale? European mainland, but in which country is it?
And because of the remarkable hardness of sapphires—9 on the Mohs scale and of aluminium oxide in general, sapphires are used in some non-ornamental applications, including infrared optical components, such as in scientific instruments; high-durability windows; wristwatch crystals and movement bearings; and very thin electronic wafers, which are used as the insulating substrates of very special-purpose solid-state electronics (especially integrated circuits and GaN-based LEDs).
They are relatively soft (2.5 to 3.0 Mohs scale), which results in reduced equipment wear, and are very white in color (averaging 98 on the Beckman scale).
The hardness of a kyanite crystal face in the long direction is 4-5 on the Mohs scale, and in the perpendicular direction it is 6-7.
These include the emery (scoring 8.0 on the Mohs scale) and Garnet (scoring 7.0).