Hardness Scale
ALTERNATIVE NAME/S: Moh’s hardness scale, Moh’s scale
DETAILS/DESCRIPTION:
To call Moh’s system for determining the hardness of minerals a ‘scale’ is actually a misnomer: it is in fact a table, since it sets out ten well-known minerals and arranges them in order of their ‘hardness,’ according to their resistance to being scratched.
Diamond comes at no. 10 as the hardest mineral, least likely to be scratched by other things. The mineral which, in 1812, German mineralogist Friedrick Moh* chose as the easiest to scratch (and no. 1 on the scale) was talc.
The scale is:
1 Talc
2 Gypsum
3 Calcite
4 Fluorite
5 Apatite
6 Orthoclase
7 Quartz
9 Corundum
10 Diamond
The scale is used as a ready-reckoner by mineralogists to calculate the relative hardness of new materials. If a specimen can be scratched by a mineral on the scale, then it is softer than that mineral; if the specimen can instead scratch it, then it is harder. A fingernail, for example, comes in at 2.5: it will scratch gypsum, but be scratched by calcite.
ONELINER: The hardness scale is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion.
OTHER CONNECTIONS: None
BIBLIOGRAPHY:
http://www.24carat.co.uk/hardnessmohsscaleframe.html