CRYSTALS: Mohs Scale

Mohs Scale of Hardness uses common crystals to show the relative hardness of stones. Talc being the softest and Diamond being the hardest to scratch or damage. This chart is from Wikipedia...and helps in identifying crystals.

Mohs 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 Feldspar (KAlSi₃O₈) 72

7 Quartz (SiO₂) 100

8Topaz (Al₂SiO₄(OH-,F-)₂) 200

9 Corundum (Al₂O₃) 400

10 Diamond (C) 1600