Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide Al2O3 with trace amounts of elements such as iron, titanium, chromium,copper, or magnesium.
Category: Oxide mineral
Formula: Aluminium oxide, Al2O3
Crystal system: Trigonal
Crystal class: Hexagonal scalenohedral
Mohs scale hardness: 9.0
Specific gravity: 4.0 ~ 4.1
Sapphire is the birthstone for September