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.