Star sapphire colors
Buying Star sapphire
Where is Star sapphire found?
Common Star sapphire Treatments
World-famous Star sapphire
Star sapphire gemology
Star sapphire legends & lore

Star sapphire colors
Star sapphire range in color from blue in various tones, pink, orange, yellow, green, lavender, gray to black. The coloring agents in blue sapphire are iron and titanium and in violet stones vanadium. A small iron content only results in yellow and green tones, chromium produces pink, iron and vanadium orange tones.

Through heat treatment at temperatures of about 1700-1800 degrees C (3100-3300 degrees F), some "cloudy" sapphires, not distinct in color, can change to a bright blue permanent color.

Buying Star sapphire
Color
The most desirable color is a vivid, intense blue.

Lighting
The silk sheen and six-rayed-star light effect shimmer best over the surface of the stone when moved in daylight, particularly around just after sunrise and before sunset.
Incandescent lights have more red light and make sapphires look less attractive.

Clarity
Included rutile needles cause the "silky shine". If such a stone is cut en cabochon it exposes the rare cat's eye effect. Oriented rutile crystal inclusions cause a six-rayed-star light effect (called asterism) to form the popular star sapphire.

Cut
Less transparent sapphires, translucent or opaque stones, are cut en cabochon to support the star effect with its six rays. The best cabochons are somewhat transparent, with smooth domes of good symmetry. One should look for an even roundness to the shape.

Star sapphire location and deposits
The most important deposits today are in Australia, Myanmar, Sri Lanka and Thailand. The most desired star sapphire used to come from Kashmir, but the deposits have apparently been depleted.

Isolated star sapphires have been found in Finland. Additional significant star sapphire deposits are in Brazil, Cambodia, China, Kenya, Madagascar. Malawi, Nigeria, Pakistan, Rwanda, Tanzania, United States (Montana), Vietnam and Zimbabwe.

Common Star Sapphire treatments
The most common treatment for star sapphire is heat treatment. Stones, generally before they are cut, are heated to between 1700 to 1800 degrees Celsius (3100-3300 degrees F) for several hours. That is just a continuation of how nature made the gemstone itself, by massive amounts of high heat. Heating improves tone and saturation of the color. A reputable dealer should always tell if a stone has been subject to heating.

Diffusion treatment exposes the surface of the stone to certain chemicals combined with heat. Generally, only the surface color changes, while the stone's body remains as is. That effect is not very desirable.
The only exception as a acceptable treatment applies for the star sapphire. The diffusion is done on the surface of the star sapphire and could extend to around a millimeter into the stone. That process supports the star effect on the gemstone. The hardness of the gemstone is not affected by the diffusion treatment.

Occasionally fractures of a star sapphire are filled with polymer or glass.
Once again, a reputable dealer should always tell if a stone has been subject to any kind of treatment.

World-famous Star sapphire
The Smithsonian Institution in Washington D.C. displays a star sapphire of more than fifty carats that was found in Sri Lanka. The mega-star of its impressive gem collection is the "Star of Asia", a star sapphire of 330 carats.
Actress Mary Pickford, on film always a decent, shy character, loved very large rubies and star sapphires. She owned both the 60-carat Star of Bombay and the 200-carat Star of India, and often wore them both at the same time.

Star sapphire gemology
Species: Corundum
Color: Blue in various tones, pink, yellow, green, lavender, gray, black
Chemical composition: Al2O3 aluminum oxide
Crystal system: (Trigonal) doubly pointy, barrel-shaped, hexagonal pyramids, tabloid-shaped
Hardness: 9 (Mohs scale)
Specific gravity: 3.95 - 4.03
Refractive index: 1.762 -1.778
Birefringence: -0.008
Color of streak: White,
Absorption spectrum: Blue s. 471, 460, 455, 450, 379; yellow 471, 460, 450, brown 471, 460-450
Fluorescence: Blue none; colorless orange-yellow, violet

The Star sapphire zodiac, myth & legend
Sapphire is the birthstone for those who are born in September. On the Zodiac chart, it is regarded as the stone for Taurus.

The ancients regarded star sapphires as a powerful talisman protecting travelers and seekers. They were considered to be so powerful, they would continue protecting the wearer even after being passed on to another person.

Abbes Hildegard von Bingen (1098-1179) chronicled the healing powers of gemstones in her book "Physica". According to her view, gemstones are formed through the powerful combination of water and fire, therefore they hold powers corresponding these phenomena. She also believed that each stone had a certain, divine blessing from God. What she said about sapphire: "Who is dull and would like to be clever, should, in a sober state, frequently lick with the tongue on a sapphire, because the gemstone's warmth and power, combined with the saliva's moisture, will expel the harmful juices that affect the intellect. Thus, the man will attain a good intellect."