Sapphire (Greek: σάπφειρος; sappheiros, 'blue stane', which probably referred instead at the time tae lapis lazuli) is a gemstane variety o the mineral corundum, an aluminium oxide (α-Al2O3). Trace amoonts o ither elements such as airn, titanium, chromium, copper, or magnesium can gie corundum blue, yellae, purpie, orange, or a greenish colour. Chromium impurities in corundum yield a pink or reid tint, the latter bein cried a ruby.