The Mohs Scale of Mineral Hardness measures one aspect of a substance's hardness: how resistant it is to being scratched.  The table that was devised is listed below.  This information can be useful when evaluating minerals to be used as gemstones and how they should best be cut to protect against being scratched. For instance, softer gemstones like turquoise can't be faceted like other harder gemstones such as diamonds or rubies. But it can be cut and polished as round beads or cabochons to be used in jewelry.

Back in 1812, German mineralogist Frederich Mohs was asked to classify a rock collection.  He devised a scale of hardness using 10 readily available minerals.  This is a very basic scale that lists the ten minerals in the order of which substance can scratch the other.  For example a diamond can scratch quartz but quartz can't scratch diamonds.  So diamonds are ranked higher than quartz.  However, the numbers Mohs assigned to the minerals are not a measure of their actual absolute scratch resistance as Mohs only had access to the limited technology of his time.  Today, however, an instrument used by mineralogists, a sclerometer, does measure the absolute hardness of minerals and this information has been added to supplement the Mohs scale.  For example, diamonds are ranked 10 on the Mohs scale and Corundum (rubies and sapphires) are ranked 9.  Using a sclerometer though it can be determined that diamonds are actually almost 4 times harder than rubies and sapphires.

Listed below is the Mohs scale along with the absolute hardness figures for the 10 minerals that Mohs used.  Additional information is also given for other gemstones, precious minerals and some common objects. Photos of the 10 minerals used in the Mohs scale are also listed below.

Hardness     Absolute     Mineral                             Additional Information

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      1                  1            Talc              Softest stone, ground to make talcum powder.

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      2                   2            Gypsum        Plaster of Paris

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      3                  9             Calcite          Limestone and shells

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      4                  21            Fluorite        Very colorful mineral

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      5                  48             Apatite         Major component of tooth enamel

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      6                  72             Orthoclase    Feldspar, Moonstone

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      7                 100            Quartz           Amethyst, Tiger's eye, Rose quartz

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      8                 200             Topaz            November birthstone

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      9                 400             Corundum     Sapphires, rubies

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     10               1500             Diamond       Hardest substance found in nature

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Hardness of some other items:

2.5                  Fingernail, Amber, Ivory

2.5-3               Gold, Silver, Copper

3                      Bronze, Coral, Pearl

4-4.5                Platinum

4-5                   Iron

5.5                    Knife blade

5.5-6                Opal, turquoise

6-7                   Glass

6.5-7                Garnet, Jade, Peridot

7.5-8                 Aquamarine, Emerald

8.5                     Cubic Zirconia

Talc and talc powder

Gypsum

Calcite

Fluorite chips

Apatite

Orthoclase

Quartz

Topaz

Corundum

Diamond