Hardness (3.04)
Diamond is the hardest natural known substance on earth and so naturally Friedrich Mohs based his hardness scale on just that.
Mohs Hardness Scale
10) diamond
9) corundum (ruby/sapphire)
8) topaz
7) quartz
6) feldspar
5) apatite
4) fluorite
3) calcite
2) gypsum
1) talc
The divisions were chosen arbitrarily and are unequal. For example the difference in hardness between 8 and 9 is much greater than the difference between any of the lower numbers. The difference in hardness is greater between 9 and 10 than between 1 and 9. Needless to say diamond is an extremely hard substance capable of resisting scratching by any other substance on earth except for diamond itself.
