Relative to each other some gemstones are harder or softer. In order to measure this, the Moh’s scale is used. The scale is from 1-10, 10 being hardest, e.g. a diamond and 1 being softest, e.g. talc. Scratching the surface with a stone of a known hardness, a scelerometer, carries out testing a stone. This is of course damaging.The scale was invented by the German scientist Mohs in 1812 and is as follows:
|
Hardness |
Mineral |
Absolute Hardness |
|
1 |
Talc(Mg3Si4O10(OH)2) |
1 |
|
2 |
Gypsum (CaSO4·2H2O) |
2 |
|
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 |
On the scale, fingernail has hardness 2.5; copper penny, about 3.5; a knife blade, 5.5; window glass, 6.5; steel file, 6.5. Using these ordinary materials of known hardness can help approximate the position of a mineral on the scale. In a gemstone jewellery context one should be particularly careful with pearls, tanzanite & emeralds. Sapphires, rubies and diamonds are always a good bet for durability though no material is impervious to sudden accidental shock. Contact us so our knowledgeable staff can advise you more. You can also click here to browse our collection of jewellery, now knowing how to assess the durability.