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Lab-created diamonds used for polishing grit, Image Credit: Leo Kenney
(See more about this image below)
History
In 1812 (or possibly 1822), the Mohs scale of mineral hardness was devised by the German mineralogist Friederich Mohs (1773-1839), who selected the ten minerals because they were common or readily available. The scale is not a linear scale, but somewhat arbitrary. The "absolute" number below is a sclerometer measurement so it gives a more accurate idea of the relative hardness of each mineral.
How to Use
To use the scale, take a mineral (or other item) of known hardness and try to scratch it with your unidentified mineral. If the unidentified mineral can scratch the known mineral, try again with a known mineral one level of hardness higher. If it can't scratch the known mineral, try again with a mineral one level of hardness lower. Keep trying and you will get an idea of how hard it is, which can be helpful in making an identification. Even if the Mohs testing does not tell you what it is, knowing its relative hardness can help you figure out what it isn't.
In addition to using the scale for mineral identification, it is also helpful for lapidary work relative to cutting and polishing.
Download and print a Mohs Quick Reference
Click here for a quick reference that you can download and print.
All of the images in the Mohs Scale table below are courtesy of and copyrighted by Jeff Scovil (except talc). Click an image to see the full picture, and click "More" below the image for additional pictures.
Mohs
Mohs
Absolute
Absolute
Mineral
Mineral
Association and Uses
Association and Uses
1
1
1
1
Talc
Talc
Used in baby powder, paper, plastic, paint, and many other products. It has even been used to help basketball players grip the ball!
Used in baby powder, paper, plastic, paint, and many other products. It has even been used to help basketball players grip the ball!
2
2
2
2
Gypsum
Gypsum
Gypsum is formed when seawater evaporates. It is used in fertilizer, plaster, and drywall, also called sheetrock. A fine-grained form called alabaster is used for sculpture.
Gypsum is formed when seawater evaporates. It is used in fertilizer, plaster, and drywall, also called sheetrock. A fine-grained form called alabaster is used for sculpture.
3
3
9
9
Calcite
Calcite
Limestone and most shells contain calcite. Trilobites, animals that are now extinct, had compound eyes made of calcite.
Limestone and most shells contain calcite. Trilobites, animals that are now extinct, had compound eyes made of calcite.
4
4
21
21
Fluorite
Fluorite
Fluorine from fluorite prevents tooth decay. The element fluorine and the term "fluorescence" actually got their names from the mineral fluorite.
Fluorine from fluorite prevents tooth decay. The element fluorine and the term "fluorescence" actually got their names from the mineral fluorite.
5
5
48
48
Apatite
Apatite
Apatite can be found in igneous, sedimentary, and metamorphic rocks and even has biological sources. A form of apatite called hydroxylapatite is in bones and teeth.
Apatite can be found in igneous, sedimentary, and metamorphic rocks and even has biological sources. A form of apatite called hydroxylapatite is in bones and teeth.
6
6
72
72
Orthoclase
Orthoclase
Orthoclase is a type of feldspar and is commonly found in granite as well as in its crystal form. It is used in scouring powder.
Orthoclase is a type of feldspar and is commonly found in granite as well as in its crystal form. It is used in scouring powder.
7
7
100
100
Quartz
Quartz
Quartz is fairly common and easy to find. Because of its piezoelectric properties (electric charge in response to pressure), quartz has been used in clocks and radios.
Quartz is fairly common and easy to find. Because of its piezoelectric properties (electric charge in response to pressure), quartz has been used in clocks and radios.
8
8
200
200
Topaz
Topaz
The November birthstone. Its natural color is mostly yellow, but because of impurities it can be brown, red, pink, orange, gray, and blue, though most blue topaz has been treated to produce the blue color.
The November birthstone. Its natural color is mostly yellow, but because of impurities it can be brown, red, pink, orange, gray, and blue, though most blue topaz has been treated to produce the blue color.
9
9
400
400
Corundum
Corundum
Sapphire and ruby are varieties of corundum. Besides the gem varieties, it is mostly used as an abrasive in sandpaper and other grinding tools.
Sapphire and ruby are varieties of corundum. Besides the gem varieties, it is mostly used as an abrasive in sandpaper and other grinding tools.
10
10
1500
1500
Diamond
Diamond
The hardest mineral on the Mohs Scale, diamonds are used in jewelry, saw blades, and as an abrasive for polishing stones.
The hardest mineral on the Mohs Scale, diamonds are used in jewelry, saw blades, and as an abrasive for polishing stones.
Mohs Test Kit
Mohs Test Kit
Pick sets are available for testing Mohs scale hardness. Each point on the picks has a different hardness and can be used to try to scratch a specimen. The points are usually made of various alloys, copper (Mohs 3), and even plastic (Mohs 2). Picks can be more accurate than using other minerals because minerals may have impurities or inclusions that may affect their ability to scratch or be scratched.
Image Credit: Marty Hart
Hardness of some other items
Hardness of some other items
Here are other minerals and objects you can use as reference items for testing. Because of variability in composition, the item's actual hardness may differ from the chart. If possible, test the objects you want to use against objects with a known hardness first.
2 - 2.5
2 - 2.5
Fingernail
2.5 - 3
2.5 - 3
Gold, Silver, Zinc
3
3
Copper (modern pennies are over 99% zinc with a thin coating of copper)
4 - 4.5
4 - 4.5
Platinum
4 - 4.5
4 - 4.5
Knife blade (ordinary steel)
4 - 5
4 - 5
Iron
6 - 7
6 - 7
Jade
7.5 - 8
7.5 - 8
Beryl
8
8
Hardened Steel
9
9
Tungsten Carbide
About the image at the top of this page
About the image at the top of this page
Lab-created Diamonds
Diamond is hardness 10 on the Mohs Scale of Mineral Hardness. Based on absolute hardness measured with a sclerometer, it is 1500 times harder than talc. This picture shows lab-created diamond grit that is used as abrasive for polishing stones. Note the size scale in the lower left corner of the image. Though sand-sized, these diamond crystals are beautifully formed.
Image Credit: Leo Kenney
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