Sapphire is a gemstone variety of the mineral corundum,an aluminium oxide (α-AI2O3). Trace amo
unts of other elements such as iron, titanium, chromium,copper or magnesium can give corundum blue, yellow, pink, purple, orange or greenish color. Chromium impurities in corundum yield a red tint, and the resultant gemstone is called a ruby.