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In 1812 a Viennese mineralogist by the name of Friedrich Mohs introduced a term called "scratch hardness" which he defined as being the resistance of a mineral when scratched with a pointed tool. To test hardness, he set up a comparison scale using ten minerals of differing hardness and his scale which became known as "Mohs scale of mineral hardness" is still used extensively today.
The softest mineral on Mohs scale of mineral hardness is Talc which is graded 1, this can be scratched by Gypsum which is 2 and Gypsum in turn can be scratched by Calcite which is 3. Each mineral on the scale is able to scratch the previous one which is less hard and in turn, it can be scratched by the one which follows which is harder. Those which are the same hardness will also scratch each other. Half grades are also used and all known minerals are allocated a place on Mohs scale of mineral hardness.
|
Hardness |
Mineral |
Example |
|
1 |
Talc |
Talcum powder |
|
2 |
Gypsum |
Colourless and used in plasters especially plaster of Paris |
|
3 |
Calcite |
|
|
4 |
Fluorite |
|
|
5 |
Apatite |
|
|
6 |
Orthoclase Feldspar |
Orthoclase / Feldspar (gemstone examples) Moonstone, Sunstone, Unakite |
|
7 |
Quartz |
|
|
8 |
Topaz |
|
|
9 |
Corundum |
|
|
10 |
Diamond |
The hardest of all gemstone varieties |
Below are some of the gemstones featured in our collection and their hardness.
Chrysocolla 2 to 2.5. Silver 2.5 to 3 hence another alloy needs to be added to it to increase its hardness. Pearl (including Mother of Pearl) 2.5 to 4.5. Serpentine 2.5 to 5.5. Coral (we only use Sponge Coral and Fossilized Coral) 3 to 4. Anhydrate (see Angelite ) 3.5. Malachite, Azurite 3.5 to 4. Rhodochrosite, Fluorite, Ammonite 4. Kyanite 4 to 7. Hemimorphite, glass 5. Obsidian 5 to 5.5. Lapis Lazuli, Turquoise, Charoite 5 to 6. Moldavite, Enstatite (see Bronzite) 5.5. Sodalite, Rhodonite, Opal, Hematite 5.5 to 6. Zoisite (see Ruby Zoisite), Sugilite, the mineral Rutile (see Rutilated Quartz), Pyrite, Prehnite, Moonstone, Labradorite, Aventurine Feldspar (see Sunstone), Amazonite 6 to 6.5. Epidote (see Unakite) 6 to 7. Tigers Eye, Peridot, Jasper, Jadeite (see Canadian Jade and Nephrite Jade), Chrysoprase, Chalcedony, Agate, Zircon, Garnet 6.5 to 7. Rose Quartz, Smoky Quartz, Quartz, Prasiolite (Green Quartz sometimes incorrectly referred to as Green Amethyst), Citrine, Aventurine, Amethyst 7. Tourmaline, Iolite 7 to 7.5. Dumortierite 7.5 to 8.5. Emerald, Beryl, Aquamarine 7.5 to 8. Topaz, Spinel 8. Sapphire, Ruby.
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| ← Misnomer | Mollusc → |
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