Mohs Scale of Hardness
What is the Mohs scale of hardness?
Mohs’ hardness is a term meaning ‘scratch hardness’ which was introduced by German mineralogist Friedrich Mohs in 1812. Mohs created a system whereby minerals were tested to their hardness with a pointed object, with 1 being the softest and 10 being the hardest. Crystals and minerals with a high number on the Mohs scale will be able to scratch those with a lower number. Crystals and minerals that have the same number won’t scratch each other.
Mohs scale of hardness test kit
Above is a sample of a crystal test kit which could include a:
- solid piece of glass (aka a glass plate)
- your fingernail
- unglazed white porcelain tile (aka a streak plate)
- unglazed black porcelain tile (aka a streak plate)
- copper coin
- magnet
- steel nail or file
- magnifying glass
- knife
Examples of crystals and minerals on the Mohs scale of hardness
|
Name |
Hardness |
Tool to test with |
|
Talc |
1 |
Fingernail will scratch |
|
Covellite |
1½ – 2 |
|
|
Stichtite |
1½ – 2½ |
|
|
Gypsum |
2 |
Fingernail will scratch |
|
Amber |
2 – 2½ |
|
|
Fuchsite |
2 – 3 |
|
|
Chrysocolla |
2 – 4 |
|
|
Gold |
2½ – 3 |
|
|
Lepidolite |
2½ – 3 |
|
|
Silver |
2½ – 3 |
|
|
Jet |
2½ – 4 |
|
|
Pearl |
2½ – 4½ |
|
|
Serpentine |
2½ – 5½ |
|
|
Calcite |
3 |
Copper coin will scratch |
|
Celestine |
3 – 3½ |
|
|
Howlite |
3 – 3½ |
|
|
Coral |
3 – 4 |
|
|
Aragonite |
3½ – 4 |
|
|
Azurite |
3½ – 4 |
|
|
Malachite |
3½ – 4 |
|
|
Shattuckite |
3½ – 4 |
|
|
Shungite |
3½ – 4 |
|
|
Fluorite |
4 |
Knife will easily scratch |
|
Rhodochrosite |
4 |
|
|
Variscite |
4 – 5 |
|
|
Kyanite |
4 – 7 |
|
|
Apophyllite |
4½ – 5 |
|
|
Charoite |
4½ – 5 |
|
|
Apatite |
5 |
Knife will scratch |
|
Scolecite |
5 – 5½ |
|
|
Bronzite |
5 – 6 |
|
|
Lapis Lazuli |
5 – 6 |
|
|
Obsidian |
5 – 6 |
|
|
Turquoise |
5 – 6 |
|
|
Moldavite |
5½ |
|
|
Brookite |
5½ – 6 |
|
|
Sodalite |
5½ – 6 |
|
|
Hematite |
5½ – 6½ |
|
|
Opal |
5½ – 6½ |
|
|
Rhodonite |
5½ – 6½ |
|
|
Feldspar |
6 |
Steel file will scratch |
|
Moonstone |
6 |
|
|
Amazonite |
6 – 6½ |
|
|
Labradorite |
6 – 6½ |
|
|
Nephrite |
6 – 6½ |
|
|
Prehnite |
6 – 6½ |
|
|
Pyrite |
6 – 6½ |
|
|
Rutile |
6 – 6½ |
|
|
Sugilite |
6 – 6½ |
|
|
Zoisite |
6 – 6½ |
|
|
Epidote |
6 – 7 |
|
|
Sunstone |
6 – 7 |
|
|
Chalcedony |
6½ – 7 |
|
|
Chrysoprase |
6½ – 7 |
|
|
Jadeite |
6½ – 7 |
|
|
Jasper |
6½ – 7 |
|
|
Kunzite |
6½ – 7 |
|
|
Peridot |
6½ – 7 |
|
| Onyx | 6½ – 7 | |
|
Garnet |
6½ – 7½ |
|
|
Agate |
7 |
|
|
Amethyst |
7 |
|
|
Aventurine |
7 |
|
|
Bloodstone |
7 |
|
|
Carnelian |
7 |
|
|
Chrysoprase |
7 |
|
|
Citrine |
7 |
|
|
Clear Quartz |
7 |
|
|
Iolite |
7 |
|
|
Mookaite |
7 |
|
|
Petrified Wood |
7 |
|
|
Quartz |
7 |
Will scratch glass (glass is a 5.5) |
|
Smokey Quartz |
7 |
|
|
Tiger Eye |
7 |
|
|
Tourmaline |
7 – 7½ |
|
|
Dumortierite |
7 – 8½ |
|
|
Aquamarine |
7½ – 8 |
|
|
Emerald |
7½ – 8 |
|
|
Topaz |
8 |
Will scratch Quartz |
|
Corundum |
9 |
Will scratch Topaz |
|
Ruby |
9 |
|
|
Sapphire |
9 |
|
|
Diamond |
10 |
Will scratch Corundum |
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