mohs hardness

MOHS HARDNESS

MOHS SCALE OF MINERAL HARDNESS

The hardness of any object is determined by the strength of chemical bonds between the constituent atoms. The hardness of a material is measured by the ease or difficulty with which it can be scratched.

Mohs´scale of mineral hardness was created in the early 19^th century by the german mineralogist Friedrich Mohs to measure hardness. He based it on ten readily available minerals. Diamond is the hardest mineral, because it can scratch all other materials. The hardness assigned to diamond is 10.0. Talc is one of the softest; almost any other mineral can scratch it. The hardness assigned to talc is 1.0.

Mineral	Hardness	Absolute Hardness (Vickers)
Talc Mg₃Si₄O₁₀(OH)₂	1	1
Gypsum CaSO₄·2H₂O	2	3
Calcite CaCO₃	3	9
Fluorite CaF₂	4	21
Apatite Ca₅(PO₄)₃(OH-,Cl-,F-)	5	48
Orthoclase KAlSi₃O₈	6	72
Quartz SiO₂	7	100
Topaz Al₂SiO₄(OH-,F-)₂	8	200
Corundum Al₂O₃	9	400
Diamond C	10	1500

A mineral´s hardness can be measured by comparing it to the hardnesses of a standardized set of minerals. The Mohs´scale of hardness is a relative scale which means that a mineral will scratch any substance lower on the scale and will be scratched by any substance higher on the scale.

Material	Mohs hardness	Vickers hardness	Shore A hardness	Brinell hardness	Knoop hardness
Gold	2,5 - 3
Sodium Bicarbonate	2,5 - 3
Cementum					40
Dentin	3 - 4	57 - 60			68
Calculus (on teeth)					86
Amalgam	4 - 5
Enamel	5	294 - 408			355 - 431
Composite resin	5 - 7
Aluminum oxide	9				2100

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