Mohs' scale of mineral hardness was created in 1812 by the German mineralogist Friedrich Mohs.

Mohs' scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. For instance, if you scratched a diamond along a pane of glass, the glass would scratch and it wouldn't harm the diamond in any way.

Mohs' scale of mineral hardness is a purely ordinal scale with, for example, Corundum being twice as hard as Topaz, but Diamond almost four times as hard as Corundum. So, a diamond is the hardest substance known to man.

Using ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale.

1 Talc

2 Gypsum

-- 2.5 Fingernail

3 Calcite

-- 3.5 Copper coin

4 Fluorite

5 Apatite

-- 5.5 Window glass/Knife blade

6 Orthoclase Feldspar

-- 6.5 Steel file

7 Quartz

8 Topaz

9 Corundum

10 Diamond