Hardness:
To determine the hardness of a stone, the Mohs scale of hardness is of an everyday usage in mineralogy.
It is made up of ten following minerals of reference:
10 – Diamond (hardest)
9 – Corundum ( Ruby-Sapphire )
8 – Topaz
7 – Quartz
6 – Feldspar
5 – Apatite
4 – Fluorite
3 – Calcite
2 – Gypsum
1 – Talc (softest)
