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www.mineralgallery.co.za Minerals P-T |
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Sapphire |
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Name
Sapphire
Chemistry
Al2O3, Aluminum Oxide
Uses
As an abrasive and as a gemstone. It is also used as a refractory material in high temperature kilns. Another interesting use is a surface treatment on special tiles used in public places where people can slip when the tiles get wet because of it's resistance to wear
Color
Blue-Saphire, Red-Ruby
Hardness
9
Crystals
It crystallizes in the trigonal system and forms hexagonal barrels or prisms with flat surfaces on both sides. It sometimes forms small triangles on the end terminations. These crystals are seen as more collectable
Accompanied by
Biotite mica, beryl, feldspar
Similar to
Tanzanite, blue spinel and blue tourmaline when faceted. In the natural it looks similar to ruby
Specific gravity
3.9-4
Sapphire is the blue variety of corundum.
Corundum is a widespread and common aluminum oxide mineral from which the gemstones ruby and sapphire, and the abrasive material emery, are made.
Common corundum, which includes all dull, opaque varieties, is usually light blue to gray, brown, or black. It occurs in feldspathoid-bearing igneous rocks as an accessory mineral, in recrystallized limestone, in placer sands, and in aluminum-rich metamorphic rocks.
The mineral is found worldwide, with the finest rubies from Myanmar (Burma) and sapphires from Southeast Asia and Australia. The red variety of corundum is known as ruby and all the other colors of corundum are known as sapphire.
Sapphire is the second hardest natural mineral known to science. The hardest mineral, diamond is still hundred and forty times harder than corundum. The hardness of sapphire can be partially attributed to the strong and short oxygen-aluminum bonds. These bonds pull the oxygen and aluminum atoms close together, making the crystal not only hard but also quite dense for a mineral made up of two relatively light elements.
The color can be white or colorless, blue, red, yellow, green, brown, purple, and pink; there are also instance of color zonation. Crystals are transparent to translucent. Sapphire's forms typical six-sided barrel shape that may taper into a pyramid, and ruby's hexagonal prisms and blades.
Imitations of the sapphires are made by a flame fusion process and are so realistic that only experts can tell the difference. Synthetic sapphires are in great demand in industry,where they are used in movements of clocks, ballpoint pens and even in high temperature furnaces.
Some natural gem-stones that look like sapphires are; blue spinel, blue tourmaline and blue zoisite-also known as Tanzanite, discovered in Tanzania. They differ in hardness and are too soft to be mistaken for the real sapphire. Buyers must be particularly weary of the Brazilian imitations which are made of clear quartz.
Famous sapphire gemstones are the magnificent 563 carat "Star of India' and the "Star of Asia"of 330 carats. The beautiful blue sapphire is highly prized and much sought after by many
