The Mohs scale of mineral hardness was created in 1812 by the German geologist and mineralogist Friedrich Mohs.
The Mohs scale rates the scratch resistance of various minerals, based on the ability of one natural mineral to scratch another. This scale is strictly an ordinal scale, in real terms diamond (10) is actually four times harder than corundum (9).
The Mohs scale uses half-numbers for in between hardness values. For example, dolomite, which scratches calcite but not fluorite, has a Mohs hardness of 3½.
| Hardness | Mineral | Description |
|---|---|---|
| 1 | Talc | Fingernail scratches it easily. |
| 2 | Gypsum | Fingernail scratches it. |
| 3 | Calcite | Copper penny scratches it. |
| 4 | Fluorite | Steel knife scratches it easily. |
| 5 | Apatite | Steel knife scratches it. |
| 6 | Feldspar | Steel knife does not scratch it easily, but scratches glass. |
| 7 | Quartz | Hardest common mineral. It scratches steel and glass easily. |
| 8 | Topaz | Harder than any common mineral. |
| 9 | Corundum | It scratches Topaz. |
| 10 | Diamond | It is the hardest of all minerals. |
