Sapphire 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. The Sapphire is one of the three gem-varieties of corundum, the other two being Ruby (defined as corundum in a shade of red) and Padparadscha (a pinkish orange variety). Although blue is their most well-known colour, Sapphires may also be colourless and they are found in many colours.