| Weight | 0.6 Cts |
| Size | 6 x 5 mm |
| Pieces | 1 |
| Shape | Pear |
| Colour | Blue |
| Clarity Grade | VS |
| Treatment | Heated |
| Country of origin | Australia |
| Mohs scale of hardness | 9.0 |
Bidding is per stone
More Information:
Sapphire (from Hebrew: Sapir) is the single-crystal form of aluminium oxide (Al2O3), a mineral known as corundum.
The corundum group consists of pure aluminium oxide. Trace amounts of other elements such as iron, titanium and chromium give sapphires their blue, yellow, pink, purple, orange or greenish color. Sapphire includes any gemstone quality varieties of the mineral corundum except the fully saturated red variety, which is instead known as ruby.
Natural sapphire
Although blue is considered the normal color for sapphire, it is found in the full range of spectral colors as well as brown, colorless, grey and black. Any sapphire other than blue or fully saturated red (ruby) is considered a fancy color sapphire.
Blue sapphire
Various shades of blue [dark and light] result from titanium and iron substitutions in the aluminium oxide crystal lattice. Some stones are not well saturated and show tones of gray. It is common to bake natural sapphires to improve color. This is usually done by heating the sapphires to temperatures of up to 1800 °C for several hours, or by heating in a nitrogen deficient atmosphere oven for 7 days or more. On magnification the silk due to included rutile needles are visible. If the needles are unbroken, then the stone was not heated. If the silk is not visible then the stone was heated adequately. If the silk is partially broken then a process known as low tube heat was used. Low tube heat is the process where the rough stone is heated to 1300 °C for 20 to 30 minutes over charcoal. This takes out any gray or brown in the stone and improves color saturation.
Fancy color sapphire
Purple sapphires are lower in price than blue ones. These stones contain the trace element vanadium and come in a wide variety of shades. Yellow and green sapphires have traces of iron which gives them their color. Pink sapphires have a trace element of chromium and the deeper the color pink the higher the value as long as the color is going toward red of rubies. Sapphires also occur in shades of orange and brown, and colorless sapphires are sometimes used as diamond substitutes in jewelry. Salmon-color padparadscha sapphires are orangy-pink, pinkish-orange, or pink-orange in color and often fetch higher prices than many of the finest blue sapphires. The word 'padparadscha' is Sinhalese for 'lotus flower'. Recently many sapphires of this color have appeared on the market as a result of a new treatment method called "bulk diffusion".
Mining
Sapphires are mined from alluvial deposits or from primary underground workings. Historically, most sapphires have been mined in Sri Lanka, Madagascar,Thailand and Myanmar. Australia leads the world in sapphire production (as of 1987) specifically from basalt derived placer deposits in Queensland and New South Wales. Pakistan, Afghanistan, India, Tanzania and Kenya also produce sapphires. The US state of Montana has produced sapphires from the El Dorado Bar deposit near Helena. Well-known for their intense, pure blue color, yogo sapphires are found in Yogo Gulch, near Utica, Montana. Gem grade sapphires and rubies are also found in and around Franklin, North Carolina, USA.
(Source wikipedia)
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