Amazing Minerals

 

Learn about the fascinating optical properties of minerals, like bi refringence (pure calcite makes an image appear doubled), polychroism (fluorite comes in many different colors), opalization (color play of opals) and fiber optic effects (ulexite, or TV stone, raises an image to the surface of the crystal). Minerals are also identified by their relative hardness. On a scale of 1-10 diamond is the hardest mineral (10), but talc is the softest (1).

Hardness	Mineral	Absolute Hardness
1	Talc (Mg3Si4O10(OH)2)	1
2	Gypsum (CaSO4·2H2O)	2
3	Calcite (CaCO3)	9
4	Fluorite (CaF2)	21
5	Apatite (Ca5(PO4)3(OH-,Cl-,F-))	48
6	Orthoclase Feldspar (KAlSi3O8)	72
7	Quartz (SiO2)	100
8	Topaz (Al2SiO4(OH-,F-)2)	200
9	Corundum (Al2O3)	400
10	Diamond (C)	1500