Aggregate hardness is referenced by the Mohs Hardness Scale. This scale assigns arbitrary quantitative units, ranging from 1 through 10, by which the scratch hardness of a mineral is determined. Each unit of hardness is represented by a mineral that can scratch any other mineral having a lower-ranking number. The minerals are ranked from talc (#1 / the softest) upward through diamond (#10 / the hardest).
Hardness |
Example Materials |
1 |
Talc |
2 |
Gypsum |
3 |
Calcite, Soft Limestone, Copper Pipe |
4 |
Fluorite, Sandstone, Marble |
5 |
Apatite |
6 |
Feldspar, River Rock, Granite |
7 |
Quartz, Hard Granite, Basalt, Trap Rock, Garnet |
8 |
Topaz, Hardened Steel |
9 |
Corundum, Hard Trap Rock, Hard Basalt, Ruby |
10 |
Diamond |
|
