Tanzanite is relatively new on the gemstone market, but has left its mark. Its blue-lavender color is rather unique and a wonderful addition to the gemstone palette. Found in Tanzania (hence the name) in 1967, it has since become a well known and widely distributed gemstone.

It has better fire than the tourmaline elbaite or peridot and an adequate hardness. Its only one direction of cleavage is somewhat of a problem because it is oriented with the direction of strongest pleochroism. This would be a problem in most gemstones because that is the direction the gemcutter would usually select to maximize the color. However, with tanzanite the color is usually strong enough anyway.

Pleochroism is very pronounced in tanzanite and is seen as three different color shades in the same stone. In the viewing a tanzanite stone, the colors dark blue, green-yellow and red-purple can be seen, all a result of pleochroism. Lesser stones may have a brownish color due to the mixing of blue, purple and green. These stones are usually heat treated to a deep blue color. Iolite is a blue-violet gemstone variety of the mineral cordierite, has strong pleochroism and can be confused with tanzanite. However, iolite is usually less strongly colored, its pleochroic colors vary from blue-violet to yellowish gray to blue and it has less fire. Iolite's unusual color shades makes it an exotic colored gemstone whose popularity is growing day by day.

VARIETY INFORMATION:

• VARIETY OF: Zoisite , Ca2Al3(SiO4)3(OH), Calcium Aluminum Silicate Hydroxide.
• USES: Gemstone
• COLOR: various shades of blue to lavender, deeper along the crystal axis.
• INDEX OF REFRACTION: 1.68 - 1.72
• BIREFRINGENCE: is good
• HARDNESS: 6.5-7
• CLEAVAGE: perfect in one direction
• CRYSTAL SYSTEM: orthorhombic