Mohs scale of mineral hardness
\n\n\n\n
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.
\n\n| Hardness | \nMineral | \nAbsolute Hardness | \n
\n| 1 | \nTalc\n(Mg3Si4O10(OH)2) | \n1 | \n
\n| 2 | \nGypsum (CaSO4·2H2O) | \n3 | \n
\n| 3 | \nCalcite (CaCO3) | \n9 | \n
\n| 4 | \nFluorite (CaF2) | \n21 | \n
\n| 5 | \nApatite\n(Ca5(PO4)3(OH-,Cl-,F-)) | \n48 | \n
\n| 6 | \nOrthoclase Feldspar (KAlSi3O8) | \n72 | \n
\n| 7 | \nQuartz (SiO2) | \n100 | \n
\n| 8 | \nTopaz\n(Al2SiO4(OH-,F-)2) | \n200 | \n
\n| 9 | \nCorundum (Al2O3) | \n400 | \n
\n| 10 | \nDiamond (C) | \n1500 | \n
\n
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.
\n\n| Hardness | \nMineral | \n
\n| 1 | \nLiquid | \n
\n| 2 | \nGypsum | \n
\n| 3 | \nCalcite | \n
\n| 4 | \nFluorite | \n
\n| 5 | \nApatite | \n
\n| 6 | \nOrthoclase | \n
\n| 7 | \nVitreous pure silica | \n
\n| 8 | \nQuartz | \n
\n| 9 | \nTopaz | \n
\n| 10 | \nGarnet | \n
\n| 11 | \nFused zirconia | \n
\n| 12 | \nFused alumina | \n
\n| 13 | \nSilicon carbide | \n
\n| 14 | \nBoron carbide | \n
\n| 15 | \nDiamond | \n
\n
Category:Materials science
