Sapphire (;
sappheiros, 'blue stone', which probably referred instead at the time to
lapis lazuli) is a typically blue
gemstone variety of the mineral
corundum, an
aluminium oxide . Trace amounts of elements such as
iron,
titanium,
chromium,
copper, or
magnesium can give corundum respectively blue, yellow, purple, orange, or green color. Chromium impurities in corundum yield pink or red tint, the latter being called
ruby.