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Hardness Tables

Mohs Hardness Scale

Hardnes Number Original Scale Modified Scale
1 Talc Talc
2 Gypsum Gypsum
3 Calcite Calcite
4 Fluorite Fluorite
5 Apatite Apatite
6 Orthoclase Orthoclase
7 Quartz Vitreous Silica
8 Topaz Quartz or Stellite
9 Corundum Topaz
10 Diamond Garnet
11 ............... Fused Zirconia
12 ............... Fused Alumina
13 ............... Silicon Carbide
14 ............... Boron Carbide
15 ............... Diamond

Hardness of Materials

Substance Number Substance Number
Agate 6-7 Indium 1.2
Alabaster 1.7 Iridium 6-6.5
Alum 2-2.5 Iridosmium 7
Aluminum 2-2.9 Iron 4-5
Alundum 9+ Kaolinite 2.0-2.5
Amber 2-2.5 Lead 1.5
Andalusite 7.5 Lithium 0.6
Anthracite 2.2 Loess (0°) 0.3
Antimony 3.0-3.3 Magnesium 2.0
Apatite 5 Magnetite 6
Aragonite 3.5 Manganese 5.0
Arsenic 3.5 Marble 3-4
Asbestos 5 Meerschaum 2-3
Asphalt 1-2 Mica 2.8
Augite 6 Opal 4-6
Barite 3.3 Orthoclase 6
Bell-metal 4 Osmium 7.0
Beryl 7.8 Palladium 4.8
Bismuth 2.5 Phosphorus 0.5
Boric Acid 3 Phosphorbronze 4
Boron 9.5 Platinum 4.3
Brass 3-4 Plat-iridium 6.5
Cadmium 2.0 Potassium 0.5
Calamine 5 Pumice 6
Calcite 3 Pyrite 6.3
Calcium 1.5 Quartz 7
Carbon 10.0 Rock Salt (halite) 2
Carborundum 9-10 Ross' Metal 2.5-3.0
Cesium 0.2 Rubidium 0.3
Chromium 9.0 Ruthenium 6.5
Copper 2.5-3 Selenium 2.0
Corundum 9 Serpentine 3-4
Diamond 10 Silicon 7.0
Diatomaceous Earth 1-1.5 Silver 2.5-4
Dolomite 3.5-4 Silver Chloride 1.3
Emery 7-9 Sodium 0.4
Feldspar 6 Steel 5-8.5
Flint 7 Stibnite 2
Fluorite 4 Strontium 1.8
Galena 2.5 Sulfur 1.5-2.5
Gallium 1.5 Talc 1
Garnet 6.5-7 Tellurium 2.3
Glass 4.5-6.5 Tin 1.5-1.8
Gold 2.5-3 Topaz 8
Graphite 0.5-1 Tourmaline 7.3
Gypsum 1.6-2 Wax (0°) 0.2
Hematite 6 Wood's Metal 3
Hornblende 5.5 Zinc 2.5


Comparison of Hardness Values of Various Materials
on Mohs and Knoop Scales

Material Formula Mohs Value Knoop Value
Talc 3MgO-4SiO2-H2O 1 ...
Gypsum CaSO4-2H2O 2 32
Cadmium Cd ... 37
Silver Ag ... 60
Zinc Zn ... 119
Calcite CaCO3 3 135
Fluorite CaF2 4 163
Copper Cu ... 163
Magnesia MgO ... 370
Apatite CaF2-3Ca3(PO4)2 5 430
Nickel Ni ... 557
Glass (soda lime) ................................. ... 530
Feldspar (orthoclase) K2O-Al2O3-6SiO2 6 560
Quartz SiO2 7 820
Chromium Cr ... 935
Zirconia ZrO2 ... 1160
Beryllia BeO ... 1250
Topaz (AIF)2SiO4 8 1340
Garnet Al2O3-3FeO-3SiO2 ... 1360
Tungsten Carbide Alloy WC, Co ... 1400-1800
Zirconium Boride ZrB2 ... 1550
Titanium Nitride TiN 9 1800
Tungsten Carbide WC ... 1880
Tantalum Carbide TaC ... 2000
Zirconium Carbide ZrC ... 2100
Alumina Al2O3 ... 2100
Beryllium Carbide Be2C ... 2410
Titanium Carbide TiC ... 2470
Silicon Carbide SiC ... 2480
Aluminum Boride AlB ... 2500
Boron Carbide B4C ... 2750
Diamond C 10 7000