Sapphire jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of very special-purpose solid-state electronics (especially integrated circuits and GaN-based LEDs). Sapphire is the birthstone for September and the gem of the 45th anniversary.
Birthstone American Gem Trade Association and Jewelers of America added spinel as an additional birthstone for August. Britain's National Association of Goldsmiths created their own standardized list of birthstones in 1937. Eastern cultures recognize a similar range of gemstones associated with birth, though rather than associating a gem with a birth month, gemstones are associated with celestial bodies, and astrology is employed to determine the gemstones most closely associated with and beneficial to a particular individual. For example, in Hinduism there are nine gemstones associated with the "Navagraha" (celestial forces including the planets, the sun, and the moon), known in Sanskrit