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.
Yogo sapphire had difficulty marketing its gems within the United States. The American Sapphire Company, which used local gemcutters from Great Falls, went bankrupt in 1909; a new firm, the Yogo American Sapphire Company, bought the American Mine, but was bankrupt by 1913. Gadsden and his wife had convinced the New Mine Sapphire Syndicate to buy out the Yogo American Sapphire Company in 1914, and in doing so, the English syndicate gained control of all known Yogo deposits. They quickly recouped the purchase price by washing the tailings left behind by previous operators of the American Mine. Montana sapphires were heavily mined