Moh’s Hardness Scale

By Becky Clark

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Some minerals are softer than others. How hard a mineral is can help identify it.

We measure the hardness of minerals by scratching them. In 1822, Frederick Mohs published his scale for determining a minerals hardness. On Mohs scale, each mineral can scratch the ones below it. Talc, for example, is softest, with a rating of 1. A diamond is hardest, with a rating of 10.

How to Perform the Test

1) Select a fresh, clean surface on

the mineral to be tested.

2) Hold the mineral firmly and attempt to scratch it.

3) Look for a scratch or line.

"Tools" for Testing HardnessThere are several simple "tools" people often have with them that can be useful in determining the hardness of an unknown mineral.QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

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Your fingernail has a hardness of 2.5.

A penny has a hardness of 3.0

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture. The steel paper clip has a hardness of about 5.5.

Mineral Scratched by Finger Nail?

Scratched by Penny?

Scratched by Paper Clip?

Number of tools that Scratched?

The following table shows the hardness of these materials:

1 Piece of chalk 3.5 Penny

2 Plaster of Paris 4 Iron Nail

2.5 Fingernail 5.5 Window Glass

3 Gold 6.5 Steel File

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SONG: MR. MOHS TOES