The gemstone sapphire

In the gem trade, sapphire refers to the blue variety of corundum. However, excluding red ruby, it scientifically encompasses all other gem varieties of corundum. (In essence, ruby is really a red sapphire, since ruby and sapphire are identical in all properties except color.)
Sapphire is the most precious of blue gemstones. It is a most desirable gem due to its color, hardness, durability, and luster. The most valuable color of sapphire is cornflower blue, known as Kashmir sapphire or Cornflower blue sapphire.

Until the last century, all sapphires (excluding blue) were called the same name as a popular gemstone of that color with the prefix "oriental" added to it. For example, green sapphire was known as "oriental emerald". The practice of applying the name of a different gemstone to identify the sapphire was misleading, so these names were virtually abolished. What was once called "oriental emerald" is now called "green sapphire". The same holds true for all other color varieties of sapphire. However, the word "sapphire" in its plain context refers only to blue sapphire, unless a prefix color is specified. Sapphire with a color other than blue is often called a "fancy" in the gem trade.

Inclusions of tiny, slender, parallel Rutile needles cause polished sapphire gems to exhibit asterism. Sapphire gems displaying asterism are known as "star sapphires", and if transparent are especially prized. Star sapphires are usually in six ray stars, but twelve ray stars are also known. Very rarely, sapphire also exhibits cat's eye effect.
Color zoning, which forms from growth layers that build up during the formation of the stone, is present in certain sapphires. However, uniformity of color is an important factor in a sapphire's value.

Colorless and pale blue sapphires from certain localities may be heat-treated to give them an intense blue color. Heat-treatment may also improve the clarity of some sapphires by removing tiny inner inclusions. Sapphire is pleochroic, displaying a lighter and more intense color when viewed at different angles. Some pleochroic sapphire is blue when viewed at one angle, and purple at a different angle.

A rare variety of sapphire, known as color changing sapphire, exhibits different colors in different light. In natural light, color changing sapphire is blue, but in artificial light, it is violet. This effect is the same phenomenon seen in alexandrite.

Sapphire was first synthesized in 1902. The process of creating synthetic sapphire is known as the Verneuil process. Only experts can distinguish between natural and synthetic sapphire.

Sapphire is a tough and durable gem, but it is still subject to chipping and fracture if handled roughly.

USES
Sapphire is one of the most popular jewelry stones. The blue variety is most often used in jewelry, but the yellow, pink, and orange stones are also popular. A rare orange-pink variety, known as padparadschah, is even more valued than blue sapphire.
Stones displaying asterism are polished as cabochons, and, if clear, are extremely valuable. Blue sapphire is sometimes carved into cameos or small figures. Synthetic sapphire is often used as a substitute for the natural material.

Sapphire is the birthstone of September.

VARIETIES
Kashmir Sapphire - Sapphire with a distinct velvety-blue color
Cornflower Sapphire - Synonym of Kashmir sapphire (above)
Cornflower Blue Sapphire - Synonym of Kashmir sapphire (above)
Star Sapphire - Sapphire displaying asterism
Padparadschah - Orange-pink variety of sapphire
Color Changing Sapphire - Sapphire exhibiting a different color in natural and artificial light
Bi-colored Sapphire - Sapphire with more than one color
Cat's Eye Sapphire - Sapphire exhibiting cat's eye effect
Fancy Sapphire - Any sapphire with a color other than blue
Verneuil Sapphire - Synthetic, laboratory-grown sapphire

Nowadays, sapphire is classified by its color in the gem trade (i.e. green color sapphire is "Green Sapphire"). Colorless sapphire is usually called "White Sapphire".

The "oriental" prefixes are not used anymore, but they are still occasionally seen. Below is a list of all the "oriental" sapphires:

Oriental Topaz - Straw yellow, gem quality sapphire
Oriental Emerald - Light to dark green, gem quality sapphire
Oriental Amethyst - Violet to pink, gem quality sapphire
Oriental Peridot - Yellow-green, gem quality sapphire
Oriental White Sapphire - Colorless, gem quality sapphire

Some other (rarely used) variety names:
Australian Sapphire - Dark blue to nearly black sapphire
Bengal Amethyst - Purple sapphire
Blue Alexandrite - Synonym of color changing sapphire
Burma Sapphire - Synthetic, laboratory-grown blue sapphire
Burmese Sapphire - Synonym of Burma sapphire (above)
Ceylon Sapphire - Light blue sapphire
Indian Topaz - Yellow to yellow-brown sapphire
King Topaz - Yellow to yellow-brown sapphire
Rose Kunzite - Synthetic pink sapphire
Star Topaz - Yellow star sapphire
Ultralite - Blue sapphire

FALSE NAMES
Brazilian Sapphire - blue tourmaline or blue topaz
Gold Sapphire - lapis lazuli with shiny pyrite sprinkles
Hope Sapphire - synthetic blue spinel
Lux Sapphire - iolite
Lynx Sapphire - iolite
Sapphire Quartz - massive blue quartz or chalcedony
Sapphire Spinel - blue spinel
Water Sapphire - iolite
Uralian Sapphire - blue tourmaline

SIMILAR GEMSTONES
Iolite, indicolite tourmaline, and blue zircon may resemble blue sapphire, but are softer. The other color varieties of sapphire are commonly confused with many gemstones, but their great hardness distinguishes them.

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ALSO SEE
The mineral Corundum
The gemstone ruby
The gemstone Iolite

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