Sapphire

Sapphire is any gemstone-quality corundum that is not red in color. (The red variety of corundum is ruby.)

When color is not specified, sapphire refers to the blue variety. Pink, yellow, green, white, and parti-color (multi-coloured) sapphires are often valued less than the blue variety of the same quality and size. However a pink-orange sapphire, called a Padparacha or Padparadja, is highly prized.

Sapphires are aluminium oxide crystals (Al₂O₃) with impurities causing the color variations.

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

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

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

In modelocked Ti-sapphire lasers, a sapphire optical crystal with titanium impurities is used to generate ultrashort pulses.

See also: List of minerals Sapphire Mountford