White sapphire is the only variety of the corundum family with no impurities in its chemical composition. The different colors that occur in sapphire are due to small amounts of aluminum oxides. That is missing in a white sapphire. It is a rare form of corundum. Stones made up of different colors, including colorless areas, are more common.
A white sapphire crystal has a pyramidal end. Some stones have bubble-like inclusions. It is generally acceptable to orient the white sapphire stone so that the color is at the base. Then, when viewed from above, color fills the stone.
6-Rayed Star White Sapphire Cabochon
A 6-rayed star white sapphire is produced when cut en cabochon. The asterism is due to the presence of needle-like inclusions in the rough crystal.
Synthetic White Sapphire
Synthetic white sapphire has been produced by the Verneuil method since about the 1920s. It has been called diamondite.
Occurrence
A white sapphire is found in Sri Lanka. Similarly, cloudy or milky sapphire also occurs there, and referred to locally as geuda sapphire. Heat treatment of geuda produces blue sapphire, much of which is faceted and used in jewelry. Some Sri Lankan corundum shows red, blue, and colorless areas, which may be faceted or polished to give an interesting stone.
White Sapphire Properties
- Specific Gravity: 4.00
- Refractive Index: 1.76-1.77
- Birefringence (DR): 0.008
- Luster: Vitreous
- Crystal Structure: Trigonal
- Composition: Aluminum Oxide
- Hardness: 9
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