Sapphire is a gemstone variety of the mineral corundum, an aluminium oxide (α-Al2O3). 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.
Along with zirconia and aluminium oxynitride, synthetic sapphire is used for shatter resistant windows in armored vehicles and various military body armor suits, in association with composites.
One type of xenon arc lamp (originally called the "Cermax" its first brand name), which is now known generically as the "ceramic body xenon lamp", uses sapphire crystal output windows that tolerate higher thermal loads – and thus higher output powers when compared with conventional Xe lamps with pure silica window.