Sapphire

Sapphire is the single-crystal form of aluminium oxide (Al2O3), a mineral known as corundum. It can be found naturally as gemstones or manufactured in large crystal boules for a variety of applications.

Sapphire gems

Sapphire is any gemstone-quality corundum. (The red variety of corundum is also known as ruby.)

Related Topics:
Gemstone - Corundum - Red - Ruby

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When color is not specified, sapphire refers to the blue variety. Pink, yellow, green, white, and parti-color (multi-colored) sapphires are often valued less than the blue variety of the same quality and size. However a pink-orange sapphire, called a padparadsha, is highly prized. They were found in many countries especially in Asia such as India, Sri Lanka, Thailand, Myanmar, and Cambodia.

Related Topics:
Color - Blue - Pink - Yellow - Green - White - Orange - Countries - Asia - India - Sri Lanka - Thailand - Myanmar - Cambodia

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It is the impurities in the aluminium oxide crystal that give the color variations, with different impurity chemical elements giving the different colors that can be found. Pure sapphire is transparent. Traces of iron and titanium give sapphires a blue color. The crystals are exceptionally hard, with only diamond being harder among natural gems. They have a hardness of 9 on the Mohs hardness scale (Diamond is 10).

Related Topics:
Hardness - Mohs hardness scale - Diamond

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Gem quality sapphires and rubies occur naturally and can be easily and cheaply produced in the laboratory. The chemical compositions and physical properties are identical to the natural sapphires. The tell-tale sign of synthetic sapphires is the crystalline growth lines which are usually curved due to the pulling during the accelerated crystal growth process.

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A version which shows an asterism is called a star sapphire (see picture above). Although natural sapphires can show an asterism, the shape of the star is usually somewhat irregular and sometimes indistinct. A manufactured star sapphire called the Linde Star shows a very regularly-shaped and distinct asterism because the formation process is more tightly controlled than the natural version.

Related Topics:
Asterism - Star sapphire - Linde

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The Logan sapphire is one of the largest blue sapphire gems known. It weighs 423 carats (84.6 g).

Related Topics:
Logan sapphire - Carat

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Lady Diana Spencer's engagement ring from Charles, Prince of Wales was a sapphire ring.

Related Topics:
Lady Diana Spencer - Charles, Prince of Wales

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Cornflower blue is one of the most popular colors for sapphires (the other choice color a deep royal blue), though there is little objective consensus about which shade of blue is the most cornflower or the most desirable.

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Sapphire is also the birthstone associated with September.

Related Topics:
Birthstone - September

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