Mar 22, 2013

How hard are rocks?

Minerals and rocks are grouped according to their chemical makeup and also by their physical features, such as color, density, grain size, splitting or cleavage lines, crystal type and hardness. The Moh scale is based on the hardness of ten well-known minerals. Each one scratches the mineral above it on the scale, and is scratched by the mineral below it:

1. Talc (a soft powder)
2. GYPSUM
3. CALCITE
4. FLUORITE
5. APATITE
6. ORTHOCLASE
7. QUARTZ
8. TOURMALINE
9. CORUNDUM
10. DIAMOND (the hardest natural substance)
(World of Science)