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MOHS HARDNESS SCALE

OLD NEW  MATERIAL ABSOLUTE
HARDNESS
1 1 talc 1
2 2 gypsum 3
3 3 calcite 9
3.5   copper penny
4 4 florspar (florite) 21
5 5 apatite 48
5.5   glass, knife steel
6 6 orthoclase, file steel 72
6.5   novaculite (silicon dioxide)
red rouge (ferric oxide)


7 vitreous pure silica
7 8 quartz 100
8 9 topaz 200
  10 garnet
8.5
green chromium oxide
  11 fused zirconium oxide
9   sapphire or corundum 400
9.2 12 fused alumina
9.3
boron
9.4-5 13 silicon carbide
9.5-6 14 boron carbide
9.7
stishovite (rare form of silicon dioxide)
Norbide (special form of silicon nitride)

9.8-9   cubic boron nitride
10 15 diamond 1500


Below is an interesting artifact, sent to me by Dr. Charles J. Di Como of  Riverdale, New York. 

It is an image of part of a letter from Fredrick Mohs to CE Wilbour in 1852. 

Mohs 1852 document


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