Mohs scale of mineral hardness
Mohs' scale of mineral hardness was created by the German mineralogist Friedrich Mohs to measure hardness.
He based it on ten readily available minerals. As it is an ordinal scale, you have to compare two minerals to decide which is harder.
The scale is neither linear nor logarithmic: for example, corundum is twice as hard as topaz, but diamond is almost four times as hard as corundum.
The absolute hardness of minerals is measured with a sclerometer[?]. One of the measures of hardness, given in the table, is the Vickers number[?] (HV). It is based on the area of the indentation after applying a standard load.
The mnemonic traditionally taught to geology students to remember this table is "The Girls Can Flirt And Other Queer Things Can Do." The table has been modified to incorporate additional substances that may fall in between two levels.
Hardness
Mineral
Absolute Hardness
1
Talc
(Mg3Si4O10(OH)2)
1
2
Gypsum (CaSO4·2H2O)
3
3
Calcite (CaCO3)
9
4
Fluorite (CaF2)
21
5
Apatite
(Ca5(PO4)3(OH-,Cl-,F-))
48
6
Orthoclase (KAlSi3O8)
72
7
Quartz (SiO2)
100
8
Topaz
(Al2SiO4(OH-,F-)2)
200
9
Corundum (Al2O3)
400
10
Diamond (C)
1500
Hardness
Mineral
1
Liquid
2
Gypsum
3
Calcite
4
Fluorite
5
Apatite
6
Orthoclase
7
Vitreous pure silica
8
Quartz
9
Topaz
10
Garnet
11
Fused zirconia
12
Fused alumina
13
Silicon carbide
14
Boron carbide
15
Diamond