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hardness of the mineral

The hardness of the mineral is measured for comparison with the represented of the ten classes of the Mohs scale (Friedrich Mohs, German mineralogist, Germode 29/1/1773 - Agordo 29/ 9/ 11839). In her a material of a certain class is grazed from those of the following classes and grazes all those of the preceding classes. In the absolute scale of the hardness (of Rosiwal), this is express in resistance to the abrasion measured in proofs from laboratory and attributing to the corindone the value 1000. Also for the Knoop scale the values of hardness are absolute, and they depend on the depth of the signs engraved on the mineral one from a special utensil with point of diamond, with which a force standard is practiced

Mohs Rosiwal and Knoop scale

mineral MOHS ROSIWAL KNOOP
talc or graphite  1  0.03  1 
gypsum or sulfur 2  1.25  32 
calcite  3  4.5  135 
fluorite  4  5  163 
apatite  5  6.5  430 
orthoclase or feldespar  6  37  560 
quartz  7  120  820 
topaz  8  175  1340 
corundum  9  1000  1800 
diamond  10  140000  7000 


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