MineCore Research and Development

Corundum is an aluminum oxide (Al2O3), which possess several desirable physical properties for commercial uses in addition to its gem stone appeal. Red corundum is better known as a ruby and gets its color from the presence of Chromium in its crystalline makeup. All other color varieties of corundum are known as sapphires and non-blue sapphires, in turn, are known as "fancy sapphires". Sapphires may be colorless or vary from deep blue, green, golden yellow, pink, reddish-orange, or violet. The most valuable color of sapphire is described as "corn-flower blue." (Black, grey, or green overtones to this vivid blue will reduce the stone's overall value).

Though still precious, blue sapphires are not as expensive as diamonds, emeralds, and rubies, with the exception of a rare variety called "Padparadscha", an orange-pink stone, as well as some pink stones. Some sapphires may contain a specific desirable inclusion that if the stone is cut in a cabochon shape, may result in an asterism ("star-shaped" inclusion). Famous sapphires of this sort include the 543-carat "Star of India," possibly the largest cut star sapphire, and the "Midnight Star," a black star sapphire, both housed at the American Museum of Natural History in New York City. The St. Edward's and Stuart sapphire are part of the British Crown Jewels and the Smithsonian owns the 330 carat "Star of Asia." See Coyle Wholesale Jewelers for more detail on famous sapphires.

Pure sapphires are overall very resilient given their high specific gravities, lack of cleavage, and 9 Moh rating on the hardness scale (diamonds are a 10). Their unique combination of physical, chemical and optical properties allows sapphires to withstand high temperatures, high pressure, thermal shock, and water or sand erosion. Sapphires are also chemically inert, with a low friction coefficient, and possess excellent electrical, optical, and dielectric characteristics. In addition, their radiation resistance makes sapphires an excellent material for use aerospace-related applications. Given these parameters, sapphires have found many commercial uses. These currently include: