| Mohs' scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material
to scratch a softer material. It was created, in 1812, by the German mineralogist Friedrich Mohs and is one of several definitions
of hardness in materials science.
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| Mohs based the scale on ten minerals that are all readily available except the last one, diamond. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch,
and/or the softest material that can scratch the given material. For example, if some material is scratched by apatite but
not by fluorite, its hardness on Mohs scale is 4.5.
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| The table below shows comparison with absolute hardness measures by a sclerometer. Mohs' is a purely ordinal scale with, for
example, corundum being twice as hard as topaz, but diamond, almost four times as hard as corundum.
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| On the Mohs scale, fingernail has hardness 2.5; copper penny, about 3.5; a knife blade, 5.5; window glass, 5.5; steel file,
6.5. Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the
scale.
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See Also