Sapphires are commonly recognized as the birthstone of September and the traditional 45th wedding anniversary gift. However, due to their physical qualities and versatility, sapphires have many applications.
Basics
These precious gemstones are formed from a mineral called corundum. They come in an assortment of colors; however, only the non-red varieties are recognized as sapphire (the red variety is ruby).
Sapphires are mined in India, Burma, Ceylon, Thailand, Vietnam, Australia, Brazil and Africa. However, since 1902, sapphires have also been synthetically created. Man-made stones remove many imperfections that true stones possess, and thus make them more applicable to science and engineering (see below).
Decorative Jewelry
The most common and obvious application for sapphires is for rings, necklaces, bracelets, earrings, and other decorative jewelry. Perhaps the most popular form of sapphire jewelry is that of the engagement ring or the eternity ring.
Sapphires' high refraction and luminosity makes them desirable. Sapphires for decorative jewelry are valued by their hue, saturation, and tone. Sometimes the stones are superheated to improve their aesthetic qualities.
Watch Faces and Crystals
The physical properties of sapphires make them ideal for watch crystals and watch faces. In addition to being glare-resistance, sapphire is the second hardest natural mineral, displaying strength up to five times as strong as glass.
Optics and Lasers
Sapphires without impurities are highly transparent between specific wavelengths of light. This makes them useful for a variety of spectroscopy or special light systems, such as infrared optics. Additionally, due to their effect on the behavior of light, Titanium-Sapphire lasers dominate the fields of ultrashort pulse generation and widely wavelength-tunable lasers. According to the Encyclopedia of Laser Physics and Technology, sapphires are invaluable to laser science because "they can easily be tuned to the required pump wavelength and allow one to work with very high pump brightness due to their good beam quality and high output power."
Outer Space
Recently, NASA has begun using sapphires to collect particles in outer space. NASA chose sapphires and other gems because their low impurity levels made it possible to detect particles and infinitesimal traces of natural elements present in solar winds. In fact, according to NPR's Day to Day, NASA used sapphires aboard the spacecraft Genesis because "aluminum layered atop sapphire was perfect for collecting noble gases such as helium and neon."
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