Mohs Hardness Scale
| Hardness | Item |
| 1 | Talc |
| 2 | Gypsum |
| 3 | Calcite |
| 4 | Fluorite |
| 5 | Apatite |
| 6 | Orthoclase Feldspar |
| 6 | Titanium |
| 7 | Quartz |
| 8 | Topaz |
| 9 | Corundum |
| 10 | Diamond |
| 2.5 to 3 | gold, silver, aluminum |
| 2.5 | fingernail |
| 4 | platinum |
| 4 to 5 | iron |
| 5.5 | knife |
| 6 to 7 | glass |
| 6.5 | iron pyrite |
| 7 to 8 | hardened steel |
