The mineral hardness scale was established by the German mineralogist Friedrich Mohs in the early 1800’s. He based the scale on ten common minerals ranging from talc, the softest mineral on the scale, to diamond, the hardest. Each mineral on the scale will scratch the mineral below it and will be scratched by the mineral above it.

Fingernails have a hardness of about 2.5. Knife blades and glass show up on the scale at about 5.5. Metal files have a hardness of about 6.5. Quartz stands at 7 on the scale.

Tourmaline gems have a hardness of about 7 to 7.5, which makes them very suitable for use as gemstones in all types of gemstone jewelry.

 

 

Hardness Material 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