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Mohs' scale of mineral hardness was created by the German mineralogist Friedrich Mohs in 1822 to measure the relative hardness or scratch resistance of various minerals. He based it on ten readily available minerals. As it is an ordinal scale, you have to compare two minerals to decide which is harder. The scale is neither linear nor logarithmic. For example, corundum is twice as hard as topaz, but diamond is almost four times as hard as corundum.

The hardness of a material is measured against the scale by finding the hardest material that that the given material can scratch, or the softest material that can scratch the given material.

Mohs original scale is as follows:

Hardness Material Absolute Hardness
1 Talc (Mg3Si4O10(OH)2) 1
2 Gypsum (CaSO4·2H2O) 3
3 Calcite (CaCO3) 9
4 Fluorite (CaF2) 21
5 Apatite (Ca5(PO4)3(OH-,Cl-,F-)) 48
6 Orthoclase (KAlSi3O8) 72
7 Quartz (SiO2) 100
8 Topaz (Al2SiO4(OH-,F-)2) 200
9 Corundum (Al2O3) 400
10 Diamond (C) 1500

To give some examples from everyday life,
a fingernail has a hardness of 2;
a copper penny, about 3;
a knife blade, 5;
window glass, 5.5;
and a steel file, 6.5.

Here are the Mohs scale ratings for 144 types of gemstones:

GemHardnessInfo Page
Diamond10Diamond Information Page
Ruby9Ruby Information Page
Sapphire9Sapphire Information Page
Star Ruby9Star Ruby Information Page
Star Sapphire9Star Sapphire Information Page
Color-Change Sapphire9Color-Change Sapphire Information Page
Chrysoberyl Cat's Eye8.5Chrysoberyl Cat's Eye Information Page
Alexandrite8.5Alexandrite Information Page
Chrysoberyl8.5Chrysoberyl Information Page
Topaz8Topaz Information Page
Rutile Topaz8Rutile Topaz Information Page
Azotic Topaz8Azotic Topaz Information Page
Mystic Topaz8Mystic Topaz Information Page
Spinel8Spinel Information Page
Imperial Topaz8Imperial Topaz Information Page
Emerald7.5 - 8Emerald Information Page
Andalusite7.5Andalusite Information Page
Hambergite7.5Hambergite Information Page
Aquamarine7.5 - 8Aquamarine Information Page
Goshenite7.5 - 8Goshenite Information Page
Cat's Eye Aquamarine7.5 - 8Cat's Eye Aquamarine Information Page
Beryl7.5 - 8Beryl Information Page
Morganite7.5 - 8Morganite Information Page
Demantoid Garnet7 - 7.5Demantoid Garnet Information Page
Quartz Cat's Eye7Quartz Cat's Eye Information Page
Amethyst7Amethyst Information Page
Cat's Eye Tourmaline7 - 7.5Cat's Eye Tourmaline Information Page
Smoky Quartz7Smoky Quartz Information Page
Quartz7Quartz Information Page
Tourmaline7 - 7.5Tourmaline Information Page
Star Lemon Quartz7Star Lemon Quartz Information Page
Rose Quartz7Rose Quartz Information Page
Ametrine7Ametrine Information Page
Kunzite7Kunzite Information Page
Citrine7Citrine Information Page
Mystic Quartz7Mystic Quartz Information Page
Paraiba Tourmaline7 - 7.5Paraiba Tourmaline Information Page
Danburite7 - 7.5Danburite Information Page
Strawberry Quartz7Strawberry Quartz Information Page
Aventurine7Aventurine Information Page
Rutile Quartz7Rutile Quartz Information Page
Chrome Tourmaline7 - 7.5Chrome Tourmaline Information Page
Dumortierite Quartz7 - 8.5Dumortierite Quartz Information Page
Iolite7 - 7.5Iolite Information Page
Rubellite Tourmaline7 - 7.5Rubellite Tourmaline Information Page
Tanzanite6.5 - 7Tanzanite Information Page
Peridot6.5 - 7Peridot Information Page
Mali Garnet6.5 - 7.5Mali Garnet Information Page
Jasper6.5 - 7Jasper Information Page
Axinite6.5 - 7Axinite Information Page
Chrysoprase6.5 - 7Chrysoprase Information Page
Fossil Coral6.5 - 7Fossil Coral Information Page
Dendritic Agate6.5 - 7Dendritic Agate Information Page
Spessartite Garnet6.5 - 7.5Spessartite Garnet Information Page
Fire Agate6.5 - 7Fire Agate Information Page
Tiger's Eye6.5 - 7Tiger's Eye Information Page
Grossularite Garnet6.5 - 7.5Grossularite Information Page
Agate Geode6.5 - 7Agate Geode Information Page
Star Rose Quartz6.5 - 7Star Rose Quartz Information Page
Ruby-Zoisite6.5 - 7Ruby Zoisite Information Page
Star Garnet6.5 - 7.5Star Garnet Information Page
Idocrase6.5Idocrase Information Page
Color-Change Garnet6.5 - 7.5Color-Change Garnet Information Page
Hiddenite6.5 - 7Hiddenite Information Page
Agate6.5 - 7Agate Information Page
Melanite6.5 - 7Melanite Information Page
Zircon6.5 - 7.5Zircon Information Page
Color-Change Diaspore6.5 - 7Diaspore Information Page
Bloodstone6.5 - 7Bloodstone Information Page
Hessonite Garnet6.5 - 7.5Hessonite Garnet Information Page
Tiger's Eye Matrix6.5 - 7Tiger's Eye Matrix Information Page
Cat's Eye Diaspore6.5 - 7Cat's Eye Diaspore Information Page
Spodumene6.5 - 7Spodumene Information Page
Tsavorite Garnet6.5 - 7.5Tsavorite Garnet Information Page
Almandine Garnet6.5 - 7.5Almandine Garnet Information Page
Peanut Wood6.5 - 7Peanut Wood Information Page
Onyx6.5 - 7Onyx Information Page
Carnelian6.5 - 7Carnelian Information Page
Pyrope Garnet6.5 - 7.5Pyrope Garnet Information Page
Chalcedony6.5 - 7Chalcedony Information Page
Rhodolite Garnet6.5 - 7.5Rhodolite Garnet Information Page
Sillimanite Cat's Eye6.5 - 7.5Sillimanite Cat's Eye Information Page
Andesine Labradorite6 - 6.5Andesine Labradorite Information Page
Star Moonstone6 - 6.5Star Moonstone Information Page
Prehnite6 - 6.5Prehnite Information Page
Labradorite6 - 6.5Labradorite Information Page
Rainbow Moonstone6 - 6.5Rainbow Moonstone Information Page
Rainbow Pyrite6 - 6.5Rainbow Pyrite Information Page
Sunstone6 - 6.5Sunstone Information Page
Moonstone6 - 6.5Moonstone Information Page
Sugilite6 - 6.5Sugilite Information Page
Clinohumite6Clinohumite Information Page
Maw-Sit-Sit6 - 7Maw-sit-sit Information Page
Cassiterite6 - 7Cassiterite Information Page
Kyanite6 - 7Kyanite Information Page
Star Sunstone6 - 6.5Star Sunstone Information Page
Jadeite6 - 6.5Nephrite Information Page
Nephrite Jade6 - 6.5Nephrite Jade Information Page
Orthoclase6 - 6.5Orthoclase Information Page
Amazonite6 - 6.5Amazonite Information Page
Cat's Eye Scapolite5.5 - 6Cat's Eye Scapolite Information Page
Moss Opal5.5 - 6.5Moss Opal Information Page
Hematite5.5 - 6.5Hematite Information Page
Nuumite5.5 - 6Nuumite Information Page
Moldavite5.5Moldavite Information Page
Opal Doublet5.5 - 6.5Opal Doublet Information Page
Fire Opal5.5 - 6.5Fire Opal Information Page
Rhodonite5.5 - 6.5Rhodonite Information Page
Scapolite5.5 - 6Scapolite Information Page
Boulder Opal5.5 - 6.5Boulder Opal Information Page
Opal5.5 - 6.5Opal Information Page
Sodalite5.5 - 6Sodalite Information Page
Hackmanite5.5 - 6Hackmanite Information Page
Sphene5 - 5.5Sphene Information Page
Lapis Lazuli5 - 6Lapis Lazuli Information Page
Tremolite-Hexagonite5 - 6Tremolite-Hexagonite Information Page
Hemimorphite5Hemimorphite Information Page
Star Diopside5 - 6Star Diopside Information Page
Smithsonite5Smithsonite Information Page
Cat's Eye Apatite5Cat's Eye Apatite Information Page
Turquoise5 - 6Turquoise Information Page
Snowflake Obsidian5 - 5.5Snowflake Obsidian Information Page
Apatite5Apatite Information Page
Chrome Diopside5 - 6Diopside Information Page
Obsidian5 - 5.5Obsidian Information Page
Tashmarine Diopside5 - 6Tashmarine Diopside Information Page
Larimar4.5 - 5Larimar Information Page
Gaspeite4.5 - 5Gaspeite Information Page
Charoite4.5 - 5Charoite Information Page
Rhodochrosite4Rhodoschrosite Information Page
Variscite4 - 5Variscite Information Page
Ammolite4Ammolite Information Page
Fluorite4Fluorite Information Page
Azurite3.5 - 4Azurite Information Page
Malachite3.5 - 4Malachite Information Page
Sphalerite3.5 - 4Sphalerite Information Page
Calcite3Calcite Information Page
Coral3 - 4Coral Information Page
Verdite3Verdite Information Page
Lepidolite2.5 - 3Lepidolite Information Page
Pearl2.5 - 4.5Pearl Information Page
Chrysocolla2 - 4Chrysocolla Information Page
Seraphinite2 - 4Seraphinite Information Page
Amber2 - 2.5Amber Information Page
  • First Published: September-16-2006
  • Last Updated: July-19-2013
  • © 2005-2014 GemSelect.com all rights reserved.
    Reproduction (text or graphics) without the express written consent of GemSelect.com (SETT Company Ltd.) is strictly prohibited.
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