A key ingredient to tanzanite's success is that it exhibits more shades of blue than a clear midnight sky, due to a phenomenon called pleochroism, whereby different colors are seen in different directions of the gemstone.
Pear-Shaped, Round
Tanzanite |
December's Birthstone |
Major Sources |
Tanzania |
Colors Found |
Shades of Lilac, Blue, Violet, and Purple as well as Green and fancy colors |
Family |
Zoisite: Ca2Al3Si3O12(OH) |
Hardness |
6.5 - 7 |
Refractive Index |
1.69 - 1.70; Biaxial (+) |
Specific Gravity |
3.35 |
Crystal System |
Orthorhombic |
Although zircon's existence predates cubic zirconia by centuries, zircon is often unfairly confused with cubic zirconia, a cheap, man-made diamond substitute. ZWhile zircon may also be used as a diamond substitute, it is valuable in its own right.
Ratanakiri, Champagne, Fancym Tanzanian
Zircon |
December's Birthstone |
Major Sources |
Australia, Burma, Cambodia, Nigeria, Sri Lanka, Tanzania, Thailand & Vietnam |
Colors Found |
Blue, Green, Honey, Red, White & Yellow |
Family |
Zircon: ZrSiO4 |
Hardness |
6.5 - 7.5 |
Refractive Index |
1.82 - 2.02; Uniaxial (+) |
Specific Gravity |
3.93 - 4.73 |
Crystal System |
Tetragonal |
Turquoise, a hydrated phosphate of copper and aluminum, is prized as a gemstone whose intense blue color is often mottled with veins of brown limonite or black manganese oxide (commonly known as spider's web turquoise). It is almost always opaque and polished as cabochons, but rare, translucent gems also exist.
Spider Web, Translucent
Turquoise |
December's Birthstone |
Major Sources |
China, India, Iran, Mexico, Tibet & USA |
Colors Found |
Bluish Green & Sky blue |
Family |
Turquoise: CuAl6(PO4)4(OH)8 |
Hardness |
5 - 6 |
Refractive Index |
1.61 - 1.65 |
Specific Gravity |
2.31 - 2.84 |
Crystal System |
Triclinic (aggregate) |
©2011 America's Collectibles Network Inc. ♦ Gerald D. Sisk, JR. ♦ Guide to Gems & Jewelery ♦ Jewelry Television™