Crystals and the Mohs Scale

Jimble Stevens

Mohs scale is a scale of the scratchability of stones when they are scratched by another substance.

1 is very soft e.g. Talc, and 10 is very hard e.g. Diamond.

It is a good guide to the general toughness of the stone and it’s ability to withstand impact or pressure..and whether you should  have it in a pouch in your pocket or if it’s fine rolling about next to your keys.

Generally, any crystal that has a Mohs rating of 6 or higher can safely be cleaned in water.

Mohs Scale of Mineral Hardness

Hardness Example
10 Diamond.
9 Corundum, Ruby, Sapphire, Star Ruby, Star Sappire, Star Ruby.
8 Beryl, Emerald, Topaz, Rutile Topaz, Imperial Topaz, Mystic Topaz, Chrysoberyl, Alexandrite.
7.5 Garnet, Goshenite, Cats Eye Aquamarine, Morganite, Beryl, Aquamarine, Emerald.
7 Clear Quartz,Tigers Eye, Amethyst, Citrine, Agate, Rose Quartz, Jasper, Citrine, Agate, Garnet, Mookite, Smoky Quartz, Tourmaline, Danburite, Ametrine, Aventurine, Rutile Quartz, Kunzite.
6
Moonstone, Labradorite, Spectrolite, Carnelian, Opalite, Peridot, Fire Opal, Star Moonstone, Jadite, Star Sunstone, Prehnite, Kyanite, Amazonite, Chrysoprase, Chalcedony, Zircon, Bloodstone.
5 Apatite, Apophyllite, Haematite, Obsidian, Cats Eye Apatite, Star Diopside, Turquoise, Lapis Lazuli, Snowflake Obsidian, Sodalite, Opal, Rhodonite.
4 Fluorite, Rhodocrosite, Ammolite, Larimar, Charoite.
3 Calcite, Celestite, Cerussite, Coral, Azurite, Malachite.
2 Selenite (Gypsum), Chrysocolla, Amber, Lepidolite, Pearl.
1 Talc.

 

To give an idea of day to day items a few handy objects that also fit in the Mohs scale are:

  • A fingernail is 2½,
  • a penny  is just under 3,
  • a knife blade is 5½,
  • glass is 5½,
  • a good steel file is 6½.

There are hardly any day to day objects that are more than a 7.