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Continue Reading about Gemstone Properties Gemstone Cleavage Gemstone Clarity Gemstone Form Gemstone Scarcity Gemstone Color Specific Gravity Luster Gemstone Crystal System |
In reality, diamond is very much harder than corundum, even though the scale says they are only one division apart. The Mohs scale is approximately linear from 1 through 9; the curve climbs sharply upward at corundum, however.
A mineral may be both hard and brittle, as in the case of diamond. Diamond will scratch any other known material, but a strong hammer blow can shatter a diamond into thousands of pieces. The perfect cleavage of diamond, in fact, allows it to be more expeditiously cut. Cleavage may be an initial diamond cutting operation, as opposed to the long and tedious process of sawing. Hardness in a gemstone will determine the degree to which it will show wear. An opal, for example, which is quite soft for a ringstone, rapidly becomes covered with fine scratches in daily use, and the polish is quickly lost. A ruby, on the other hand, will remain bright |
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and lustrous for years, because the material is harder than most of the abrasive particles in the atmosphere that contribute to gem wear.
The hardness of a material may vary slightly with composition and also with state of aggregation. The measurement of hardness is very tricky and often a mark that looks like a scratch is actually a trail of powder left by the supposedly harder material! It is really not critical whether the hardness of a mineral is 5 or 5.5. Fractional hardnesses are reported where the literature has indicated an intermediate value. A range in hardness is much more meaningful, and the values reported in this book represent all values encountered in the literature. In only one case (kyanite) does the hardness of a mineral vary very widely even within a single crystal. In most cases the hardness range reported is very small (one unit).
The hardness of a material may vary slightly with composition and also with state of aggregation. The measurement of hardness is very tricky and often a mark that looks like a scratch is actually a trail of powder left by the supposedly harder material! It is really not critical whether the hardness of a mineral is 5 or 5.5. Fractional hardnesses are reported where the literature has indicated an intermediate value. A range in hardness is much more meaningful, and the values reported in this book represent all values encountered in the literature. In only one case (kyanite) does the hardness of a mineral vary very widely even within a single crystal. In most cases the hardness range reported is very small (one unit).
Gemstone Name | Hardness | Gemstone Name | Hardness |
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Agate | 7.0 | Jet | 2.5 |
Alexandrite | 8.5 | Kunzite | 7.0 |
Amber | 2.5 | Kyanite | 7.0/5.0 |
Amethyst | 7.0 | Labradorite | 6.0 |
Ametrine | 7.0 | Lapis Lazuli | 5.5 |
Andalusite | 7.5 | Malachite | 4.0 |
Apatite | 5.0 | Moonstone | 6.0 |
Aquamarine | 7.5 | Morganite | 7.5 |
Aventurine | 7.0 | Obsidian | 5.0 |
Azurite | 3.5 | Onyx | 7.0 |
Beryl | 7.5 | Opal | 6.0 - 6.5 |
Bloodstone | 7.0 | Pearl | 3.0 |
Blue Chalcedony | 7.0 | Peridot | 6.5 |
Camelian | 7.0 | Rhodochrosite | 4.0 |
Cat's Eye - Chrysoberyl | 8.5 | Rhodonite | 6.0 |
Cat's Eye-Quartz | 7.0 | Ruby | 9.0 |
Chrysoprase | 7.0 | Sapphire | 9.0 |
Citrine | 7.0 | Sardonyx | 7.0 |
Coral | 3.5 | Scapolite | 6.0 |
Diamond | 10.0 | Serpentine | 2.5-5.0 |
Emerald | 7.5 | Sillimanite | 7.5 |
fluorite | 4.0 | Quartz | 7.0 |
Garnet | 6.5 -7.5 | Sodalite | 5.5 |
Goldenite | 7.0 | Spectrolite | 6.0 |
Goshenite | 7.5 | Spinel | 8.0 |
Heliodor | 7.5 | Sunstone | 6.0 |
Hematite | 6.5 | Tanzanite | 6.5 |
Hidden ite | 7.0 | Tiger's Eye | 7.0 |
Howlite | 3.5 | Topaz | 8.0 |
lolite | 7.0 | Tortoiseshell | 2.5 |
Ivory | 2.5 | Tourmaline | 7.5 |
Jade | 6.5 -7.0 | Turquoise (Stabilized) | 6.0 |
Jasper | 7.0 | Zircon | 7.5 |
References:
1- Color Encyclopedia of Gemstones, Joel E. Arem, VNR publications, New York.
1- Color Encyclopedia of Gemstones, Joel E. Arem, VNR publications, New York.