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Corundum Sapphire - Interesting Facts
Sapphire, means 'dear to the planet saturn' in Greek. It is a mineral known as corundum made from alumunium oxide. They are found either naturally or manufactured in large crystal boules. When you talk about sapphires, you are actually talking about blue corundum (or any other color except red), red mineral corundum is called as ruby. Sapphire can also be green, pink, orange and yellow, but the most favored color is the rich intense blue, and therefore considered the most expensive types of sapphires. The inclusions of iron and titanium within the alumunium oxide result in various blue shades. Fancy sapphires are any sapphire other than red or blue.
Sapphire Mohs Hardness Scale
Sapphire is a hard gemstone and does not cleave easily, it has a Mohs hardness of 9, just below diamonds which makes them perfect for faceted gems. Sapphires are classified among the most valuable of gems, included as one of the four most precious stones and it is one of nature's most durable gemstone. There are at least 30 blue sapphires weighing more than 100 carats has been found.
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Sapphire Heat Treatment
Most sapphires are heat treated to about 2000 degrees in order to intensify their color or clarity. This will also remove any tiny inclusions found in the stone. The heat causes dissolution of diffusion and inclusions of impurities into the surrounding corundum. Local color concentrations (patches of color) in sapphires and rubies can also be removed by heat treatment because heat allows the color-causing impurities to more evenly distribute through the crystal.
Diffusion of beryllium or similar element into the surface of the gem is another method to change the natural color of the stone. The process is by heating the gems to very close to its melting point, certain chemical powders then placed in contact with the faceted gem and diffuse into the surface of the stone. This is a far less costly treatment but the color of some diffused treated gems may be effected by repolishing or recutting of the gem. Diffusion treatment will also modify the refractive index of the gem and cause color concentration at facet junctions. Since the treatments will modify the natural inclusions of the gems, thus the detection of diffusion and heat treatment is possible.
- July Birthstone
When the color of the corundum stone turns red, then it is called Ruby, the birthstone for July.
- November Birthstone
Topaz, the birthstone for November is listed as the 4th hardest gemstone just after diamond, corundum and crysoberyl.
- Zodiac Sign of Libra
Sapphire is associated with the Libra sun sign.
Sapphire Meaning and Symbolism
These stones have been treasured for thousand of years and it is believed by ancient Persians that the earth rested on a big giant sapphire and the blue color of the sky is due to its reflection. Sapphire has long symbolized truth, faithfulness and sincerity. It is also considered as the precious stone that brings prosperity and good luck to the wearer. A gift of a sapphire was a pledge of trust, purity, honesty and loyalty in ancient times. This tradition makes saphire a popular choice for engagement rings. They were the gemstone of choice for high priests and kings. Prince Charles chose a sapphire engagement ring for Princess Diana.
Where Sapphires are Found
Historically, most sapphires have been mined in Madagascar, Sri Lanka and Myanmar. Now, Australia leads the world in sapphire production. Afghanistan, Tanzania, Burma, Thailand, Pakistan, India and Kenya also produce sapphires. Sapphire is the September birthstone and folks who are under the zodiac signs Virgo and Taurus also favored the sapphire as their birthstone.