Mineral | Corrundum |
---|---|
Chemistry | Al2O3 |
Color | Light - Deep Blue |
Refractive Index | 1.762 - 1.770 |
Birefringence | 0.008 - 0.010 |
Specific Gravity | 4.00 |
Mohs Hardness | 9.0 |
Sapphires have a long history of being regarded as gemstones of nobility and elegance, often used in jewelry by European royal families since the Middle Ages. Sapphires are a variety of corundum and come in various colors, with blue sapphires being the most famous and highly prized.
Mineral | Corrundum |
---|---|
Chemistry | Al2O3 |
Color | Light - Deep Blue |
Refractive Index | 1.762 - 1.770 |
Birefringence | 0.008 - 0.010 |
Specific Gravity | 4.00 |
Mohs Hardness | 9.0 |
Color is the most important factor in determining the value of a blue sapphire. The closer the color is to a pure blue with vivid saturation, the higher the value. Dark sapphires are less valuable, while lighter or overly saturated stones may also have reduced value. Inclusions can affect the price of sapphires. While inclusions generally lower the price, some rare sapphires with specific inclusions, like those from Kashmir, can increase in value. Carat weight also affects the value, with larger stones being rarer and more expensive. The average price per carat for a blue sapphire is around $300, but it can range from $100 to $500 per carat depending on quality.
Sapphires exhibit a range of blue hues, often with violet or green undertones. Desirable color grades include "Royal Blue" and "Cornflower Blue," with Royal Blue being a true blue with purplish-tinged hues and Cornflower Blue resembling the blue of cornflowers.
High-quality blue sapphires are found in several locations around the world, with notable sources including: Sri Lanka: Known for producing blue sapphires of all colors. Kashmir: Sets the standard for evaluating blue sapphires, known for their velvety texture and purplish-blue hues. Australia: Known for darker sapphires, but some fine examples are found. Myanmar (Burma): Produces high-quality violet-blue sapphires. Thailand: Known for producing blue sapphires with fine hue and saturation. Montana (USA): Known for Montana sapphires, often steely gray but with exceptions like Yogo Gulch sapphires.
Sapphires usually contain inclusions, but they are typically of higher clarity compared to rubies. Inclusions in sapphires can include elongated mineral inclusions called needles, rutile needle inclusions that create asterism (a star-like effect), crystals, fingerprint inclusions, color gamut, and color bands. Blue sapphires often exhibit asterism, which is caused by rutile needle inclusions reflecting light to create a six-rayed star pattern.
Clean blue sapphire jewelry with warm soapy water and a soft brush, avoiding mechanical cleaning methods that can damage the stone. A paste made of baking soda and water can be used for more stubborn dirt. Rinse well and dry with a soft cloth.