Friedrich Mohs was a German mineralogist who designated a scale for mineral hardness based on the ability to scratch or to be scratched. The higher the scale value the harder the mineral.
The original scale ranged from 1 to 10.
An expanded scale ranged from 1 to 15.
|
Mineral |
Original Scale |
Expanded Scale |
Hardness |
|
talc |
1 |
1 |
very soft |
|
gypsum |
2 |
2 |
|
|
calcite |
3 |
3 |
|
|
fluorite |
4 |
4 |
|
|
apatite |
5 |
5 |
|
|
orthoclase |
6 |
6 |
|
|
vitreous silica |
|
7 |
|
|
quartz |
7 |
8 |
|
|
topaz |
8 |
9 |
|
|
garnet |
|
10 |
|
|
fused zirconia |
|
11 |
|
|
fused alumina, corundum |
9 |
12 |
|
|
silicon carbide |
|
13 |
|
|
boron carbide |
|
14 |
|
|
diamond |
10 |
15 |
extremely hard |
where:
• Corundum is aluminum oxide. A ruby or sapphire are forms of corundum that are clear.
