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.

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

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
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