Tanzanite

Tanzanite was enthusiastically celebrated as "Gemstone of the 20th Century" after its discovery in 1967. It is named after the East African state of Tanzania where its only deposit has been found. The legendary New York jewelers Tiffany & Co were the first to promote tanzanite as a fine gemstone. Tanzanite is a variety of the zoisite species. In good quality the color is ultramarine to sapphire blue. The most popular color is a saturated blue, which shows a purplish hue shimmering around it. Tanzanite needs experienced cutters to treat it carefully, as the stone has perfect cleavage in one direction. The stone is cut in all imaginable shapes and forms, from classical round cuts to imaginative designer cuts. Nearly all tanzanite has been heat treated to produce the striking violet-blue color. Due to its minor hardness (6.5-7 on Mohs scale) tanzanite is not especially durable. Therefore it should be worn with care. Tanzanite has become so popular that in October of 2002 the American Gem Trade Association (AGTA) announced that tanzanite had joined zircon and turquoise in the list of birthstones for the month of December. In good quality, the color is ultramarine to sapphire blue. The most popular color is a saturated blue, which shows a purplish hue shimmering around it. Due to its minor hardness (6.5-7 on Mohs scale) tanzanite is not very resistant. Therefore it should be worn with care, and should never be cleaned by ultrasonic methods. As the stone is found in only one location, it is especially rare.

The most popular color is a saturated blue, which shows a purplish hue shimmering around it. Typical for tanzanite is the appearance of several colors in one and the same stone (pleochroism), which means, depending on the perspective, the stone appears blue, purple, brown or yellow. In artificial light tanzanite color appears more amethyst blue.

Tanzanite is a transparent gem, and eye clean specimens can often be found. Tanzanite cat's eyes are rare. Tanzanite needs experienced cutters to treat it carefully, as it has perfect cleavage in one direction. The stone is cut in all imaginable shapes and forms, from classical round cuts to imaginative designer cuts.

The only known deposit of tanzanite is a five square mile hilltop at Merelani Hills near Ausha, ten miles south of the Kilimanjaro International Airport in Tanzania. Most rough crystals show a large proportion of brownish-yellow tints, which vanish when heated to 752-932 degrees F (400-500 degrees C).

Tanzanite gained worldwide fame as a fine and rare gemstone in itself. Tanzanites in especially good qualities and larger sizes are in serious demand and command high prices. It isn't only the spectacular color. Since the stone is found in only one special location in the entire world, it is especially rare.

Tanzanite Gemology
Species: Zoisite
Color: Sapphire blue, amethyst, violet
Chemical composition: Ca2Al3(Sio4)3(OH) calcium aluminum silicate
Crystal system: Orthorhombic, multifaceted prisms, mostly striated
Hardness: 6.5-7 (Mohs scale)
Specific gravity: 3.35
Refractive index: 1.691 - 1.700
Birefringence: +0.009
Absorption spectrum: 595, 528, 455
Fluorescence: None

Too new to have written a page for itself in the books of myth, history, wisdom, the zodiac scheme or the relation between planets and mankind, still tanzanite has left its mark in present time.