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)
