HARDNESS
The hardness of a gemstone can be defined as its ability to
resist scratching. It is therefore an important property: it shows how a gem
will withstand daily use, all that will begin its surface.
Precious stones are classified according to a hardness scale
ranging from 1 to 10, established by the Austrian mineralogist “Mohs Frederich”.
The comparative scale implies that a stone with hardness can scratch up a stone
of lesser hardness or be scratched by another of higher hardness. Thus,
corundum (9.0) easily scratch topaz (8.0) but will be scratched by diamonds
(10.0). This scale is relative to the extent that it gives no indication of
variations of a hardness level to another. However, it is estimated that the diamond
(10) is 140.000 times harder than corundum (9) which in turn is about 1000
times harder than topaz (8).
Hardness of gems and minerals
|
Gem / Mineral
|
Hardness
|
|
Actinolite
|
5.0 - 6.0
|
|
Aquamarine
|
7.5
|
|
Alexandrite
|
8.5
|
|
Almandine
|
7.5
|
|
Amblygonite
|
5.5 - 6.0
|
|
Amber
|
2.0
|
|
Amethyst
|
7.0
|
|
Analcime
|
5.0 - 5.5
|
|
Andalusite
|
7.5
|
|
Apatite
|
5.0
|
|
Augelite
|
5.0
|
|
Beryllonite
|
5.5 - 6.0
|
|
Brazilianite
|
5.5
|
|
Brookite
|
5.5 - 6.0
|
|
Bustamite
|
5.5 - 6.5
|
|
Chalcedony
|
6.5 - 7.0
|
|
Calcite
|
3.0
|
|
Celestite
|
3.0 - 3.5
|
|
Chrysoberyl
|
8.5
|
|
Chrysocolla
|
2.0 - 5.5
|
|
Chrysoprase
|
6.5 - 7.0
|
|
Citrine
|
7.0
|
|
Cordierite
|
7.5
|
|
Datolite
|
5.0 - 5.5
|
|
Demantoid
|
6.5 - 7.0
|
|
Diamond
|
10.0
|
|
Diopside
|
5.0 - 6.0
|
|
Dioptase
|
5.0
|
|
Durangite
|
5.0
|
|
Emerald
|
7.5
|
|
Enstatite
|
5.5
|
|
Euclase
|
7.5
|
|
Eudialyte
|
5.0 - 5.5
|
|
Fluorite
|
4.0 - 4.5
|
|
Grossular
|
7.5
|
|
Hauynite
|
5.5 - 6.0
|
|
Herderite
|
5.0
|
|
Hornblende
|
5.0 - 6.0
|
|
Kunzite
|
6.0 - 7.0
|
|
Kyanite
|
4.0 - 5.0 - 7.0
|
|
Manganotantalite
|
6.0
|
|
Malachite
|
3.5 - 4.0
|
|
Mesolite
|
6.0
|
|
Milarite
|
5.5 - 6.0
|
|
Natrolite
|
5.0 - 5.5
|
|
Obsidian
|
5.0 - 6.0
|
|
Orthoclase
|
6.0 - 6.5
|
|
Peridot
|
6.5 - 7.0
|
|
Pyrope
|
7.5
|
|
Pyroxmangite
|
5.5 - 6.0
|
|
Quartz
|
7.0
|
|
Rhodonite
|
5.5 - 6.5
|
|
Ruby
|
9.0
|
|
Sapphire
|
9.0
|
|
Scolecite
|
5.0
|
|
Serpentine
|
2.5
|
|
Smithsonite
|
5.5
|
|
Spessartine
|
7.5
|
|
Spinel
|
8.0
|
|
Stibiotantalite
|
5.5
|
|
Tanzanite
|
6.5 - 7.0
|
|
Topaz
|
8.0
|
|
Tourmaline
|
7.5
|
|
Tremolite
|
5.0 - 6.0
|
|
Uvarovite
|
7.5
|
|
Wardite
|
5.0
|
|
Yag
|
8.0
|
|
Zircon
|
6.5 - 7.5
|
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