Difference between revisions of "Tanzanite"
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− | Tanzanite, | + | Tanzanite, a variety of [[zoisite]], was discovered in the Merelani district of Tanzania near Mount Kilimanjaro in 1967. So far, all tanzanite discovery has been limited to a six kilometer strip in this area, which was divided into four blocks, labeled A, B, C and D. Block C is the only site still commercially producing rough tanzanite at this time. |
− | All purple and blue varieties of the stone are the result of heat treatment. The stone is a yellowish-brown "bug juice" color when it is mined, but when heated to between 800-900 degrees Fahrenheit, it becomes that gorgeous violet blue that is used in jewelry. The stone has never been found in another locality, so it is indeed a depleting resource. It is somewhat soft (6-7 on | + | All purple and blue varieties of the stone are the result of heat treatment. The stone is a yellowish-brown "bug juice" color when it is mined, but when heated to between 800-900 degrees Fahrenheit, it becomes that gorgeous violet blue that is used in jewelry. The stone has never been found in another locality, so it is indeed a depleting resource. It is somewhat soft (6-7 on Mohs scale of hardness) and has a direction of cleavage along which it can be easily broken. It is desirable because of its elegant, opulent color. |
Revision as of 20:59, 23 December 2006
Tanzanite | |
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Chemical composition | Calcium aluminum silicate |
Crystal system | Orthorhombic |
Habit | Prismatic |
Cleavage | Perfect, prismatic |
Fracture | Uneven |
Hardness | 6.5 |
Optic nature | Biaxial + |
Refractive index | 1.685-1.707 |
Birefringence | 0.008 |
Dispersion | Low, 0.012 |
Specific gravity | 3.35 |
Lustre | Vitreous |
Pleochroism | Strong trichroism (dichroism in heated) |
Tanzanite, a variety of zoisite, was discovered in the Merelani district of Tanzania near Mount Kilimanjaro in 1967. So far, all tanzanite discovery has been limited to a six kilometer strip in this area, which was divided into four blocks, labeled A, B, C and D. Block C is the only site still commercially producing rough tanzanite at this time.
All purple and blue varieties of the stone are the result of heat treatment. The stone is a yellowish-brown "bug juice" color when it is mined, but when heated to between 800-900 degrees Fahrenheit, it becomes that gorgeous violet blue that is used in jewelry. The stone has never been found in another locality, so it is indeed a depleting resource. It is somewhat soft (6-7 on Mohs scale of hardness) and has a direction of cleavage along which it can be easily broken. It is desirable because of its elegant, opulent color.