Hardness

In 1812, German mineralogist Fredirich Mohs arranged 10 minerals on a scale of 1 to 10. Each mineral on this scale could only scratch the mineral that appeared below it. Mohs' method of measuring the hardness of minerals was adopted by science and it remains the standard today. A human fingernail rates about 2.5 on the Mohs Scale, while a penknife rates about 5.5.

The Mohs Scale

1. Talc

2. Gypsum

3. Calcite

4. Fluorite

5. Apatite

6. Feldspar

7. Quartz

8. Topaz

9. Corondum

10. Diamond

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