Sapphire

Sapphire (Greek: σάπφειρος; sappheiros, 'blue stone', which probably referred at the time to lapis lazuli instead) is a gemstone variety of the mineral corundum, an aluminium oxide (α-Al₂O₃). Trace amounts 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.