FACTOID # 10: The total number of state executions in 2005 was 60: 19 in Texas and 41 elsewhere. The racial split was 19 Black and 41 White.
 
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Encyclopedia > Mohs hardness scale

Mohs' scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. It was created by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science.


Mohs based the scale on ten readily available minerals. Materials are characterised against the scale by finding the hardest material that they can scratch.


The table below shows comparison with absolute hardness measures by a sclerometer. Mohs' is a purely ordinal scale with, for example, corundum being twice as hard as topaz, but diamond, almost four times as hard as corundum.

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 Orthoclase Feldspar (KAlSi3O8) 72
7 Quartz (SiO2) 100
8 Topaz (Al2SiO4(OH-,F-)2) 200
9 Corundum (Al2O3) 400
10 Diamond (C) 1500

The mnemonic traditionally taught to geology students to remember this table is "The Girls Can Flirt And Other Queer Things Can Do."


An alternative table is shown below which has been modified to incorporate additional substances that may fall in between two levels.

Hardness Mineral
1 Liquid
2 Gypsum
3 Calcite
4 Fluorite
5 Apatite
6 Orthoclase
7 Vitreous pure silica
8 Quartz
9 Topaz
10 Garnet
11 Fused zirconia
12 Fused alumina
13 Silicon carbide
14 Boron carbide
15 Diamond

  Results from FactBites:
 
Mohs Hardness Scale (528 words)
Mohs' scale of mineral hardness quantifies the scratch resistance of minerals by comparing the ability of a harder material to scratch a softer material.
The Mohs scale was invented in 1812, by the German mineralogist Friedrich Mohs.
With the Mohs Scale, the hardness of a material is measured against the scale by finding the hardest material that it can scratch, and/or by identifying the softest material that can scratch it.
Baxter’s The Jewellers, Birthstone Information (2514 words)
On the Mohs scale of hardness aquamarine measures 7-5 to 8 and is therefore a durable stone.
Sapphire and ruby have a hardness of 9 on the Mohs scale.
Mohs' scale of hardness was developed by Friedrich Mohs (1773-1839) and measures the hardness of "rock" on a scale of 1 to 10.
  More results at FactBites »

 
 

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