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Minerals Identification: MOHS SCALE OF MINERAL HARDNESS


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Friedrich Mohs (1773-1839)

German geologist/mineralogist.

Mohs, studied chemistry, mathematics and physics. He started classifying minerals by their physical characteristics, in spite of their chemical composition, as it was done before. He created a hardness scale that is still used as Mohs scale of mineral hardness.

MOHS SCALE OF MINERAL HARDNESS

 Hardness Mineral Everyday equivalent

10

Diamond

synthetic diamond

9

Corundum

ruby

8

Topaz

sandpaper

7

Quartz

steel knife

6

Orthoclase/Feldspar

penknife blade

5

Apatite

glass

4

Fluorite

iron nail

3

Calcite

bronze coin

2

Gypsum

fingernail

1

Talc

baby powder

The scale goes from 1 to 10. Diamond is at the top of the scale, with a rating of 10, Talc is the softest, with a rating of 1. You can use minerals of known hardness to determine the relative hardness of any other mineral. A mineral of a given hardness will scratch a mineral of a lower number. For example one of your fingernail(2) can scratch a talc(1) specimen or with a broken glass(5) you can scratch a calcite(3) or fluorite(4) specimen.

 

To use the hardness scale, try to scratch the surface of an unknown sample with a mineral or substance from the hardness scale (these are known samples). If the unknown sample cannot be scratched by calcite (3) but it can be scratched by fluorite(4), then it's hardness is between 3 and 4. An example of minerals that have a hardness between 3 and 4 are barite, celestite and cerussite(3 to 3.5). You can use this test to distinguish between calcite and barite or between barite and fluorite.

 

If you wish to test an unknown mineral for hardness remember that the minerals can be damaged and lose value if not scratched properly.

Some GEMSTONES hardness

Hardness Gem

10

Diamond

9

Sapphire, Ruby

8.5

Crysoberyl, Alexandrite, Cats eye

7.5 - 8

Beryl, Emerald, Aquamarine

7.5

Zircon

7 - 7.5

Tourmaline (Elbaite, Dravite)

7

Quartz (Amethyst, Citrine)

6.5 - 7.5

Garnet (Hessonite, Rhodolite, Spessartine)

GEMSTONES

Mostly gemstones have a hardness of 7 or more. But there are some gemstones with lower hardness for example Jade(6.5), Lapislazuli(5-5.5), Opal(5.5-6.5), Turquoise(5-6) or Feldspars(6-6.5) like Labradorite, Amazonite, Moonstone, or Sunstone



Another MINERALS hardness

Hardness Minerals

9

Sapphire

7.5 - 8

Beryl

6.5 - 7

Olivine (Peridot), Jade, Spodumene (Kunzite), Epidote, Cassiterite

6 - 6.5

Iron Pyrite, Rutile, Albite, Prehnite, Benitoite, Epidote, Cassiterite

5 - 6

Turquoise, Hematite, Augite, Diopside, Moldavite

5 - 5.5

Goethite, Natrolite, Datolite, Analcime, Wollastonite

4.5 - 5

Apophyllite, Scheelite

4 - 4.5

Platinum, Smithsonite, Wolframite

3.5 - 4

Aragonite, Ankerite, Dolomite, Azurite, Malachite, Sphalerite, Chalcopyrite, Cuprite, Rhodochrosite, Strontianite, Stilbite, Heulandite, Mimetite

3 - 3.5

Barite, Celestite, Cerussite, Atacamite

3

Wulfenite, Vanadinite, Bornite

2.5 - 3

Gold, Silver, Copper, Galena, Anglesite, Mica Phlogopite

2.5

Micas (Biotite,Lepidolite)

2 - 2.5

Cinnabar, Amber, Mica Muscovite

2

Sulfur

1.5 - 2

Molybdenite

1 - 2

Aurichalcite



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