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General Info ‣ Moh's Hardness Scales

One of the major factors which govern the choice and design of size reduction machines, air classifiers, mixers and dryers, etc. is the hardness of the material to be processed.

As general rule, the hardness is defined in accordance with Moh’s scale of hardness, which divided into 10 grades of Hardness.


Hardness
01 – 03
=
Soft
Hardness
3.5 – 05
=
Medium
Hardness
05 – 10
=
Hard


Material

Hardness

Material

Hardness

Anhydrate
03 – 3.5
Kaolin
02
Anthracite
02 – 2.5
Chalk / Limestone
03
Apatite
05
Corundum
09
Asbestos
03
Magnesite
04 – 4.5
Baryte
03 – 3.5
Magnetite
5.5 – 6
Basalt
08
Marble
03
Bentonite
01
Pitchblende
04 – 6
Boron Carbide
9.5
Pyrite
06 – 6.5
Boron Notride, cubic
9.7
Quartz
07
Calcite
03
Red Iron Ore
5.5 – 6.5
Diamond
10
Rhodonite
05 – 6.5
Dolomite
3.5 – 04
Rutile
06 – 6.5
Siderite
04 – 4.5
Sulfur
1.5 – 02
Colored Clays
01 – 02
Pearl White
03 – 3.5
Feldspar
06
Silicon Carbide
09
Fluorite
04
Steatite
01
Gypsum
1.5 – 02
Rock Salt
02
Mica
2.5
Talcum
01
Garnet
6.5 – 7.5
Zirconium Oxide
8.5
Granite
07
Zircon Sand
7.5
Graphite
01
Tungsten Carbide
8.5