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 Montana sapphire mines have been less successful because they have few blue sapphires and non-blue sapphires have low profit margins. These gems inspired the names of features: the mountains near Rock Creek are known as the Sapphire Mountains. Garnets are also found at some Montana sapphire sites, inspiring the name of the Garnet Range, which lies to the north of the Sapphire Mountains. In 1969, the sapphire and agate were jointly declared Montana's two official state gemstones. Mining of Yogo sapphires was exceptionally difficult and remains sporadic today. Even so, Yogo sapphire mining turned out to be more valuable than