Skip to main content Tanzanite | Boston Gems

Treatment / Enhancement

Tanzanite is the blue-violet or violet-blue form of the mineral Zoisite. Most Tanzanite is brown or green when mined and is heat treated to bring out the beautiful blue and purple hues. This treatment is permanent and is accepted in the trade. Tanzanite has been imitated using synthetic Forsterite, synthetic Spinel, cubic Zirconia, and glass.


Tanzanite was discovered in 1967 in the Merelani Hills of northern Tanzania which is the only location where it can be found. It is a pleochroic gemstone, meaning it shows different colors depending on the viewing direction. Therefore, the type of cut is important in order to emphasize the best range of color.


Tanzanite was named in honor of Tanzania where it was first found. The story told of the discovery is that a Masai tribesman came upon a beautiful blue cluster of crystals that had weathered out of the rock in the hills near Mount Kilimanjaro. He then shared it with miners, eventually leading to distribution and promotion by Tiffany & Co. Tanzanite became a secondary birthstone for December. Its vivid saturated colors can inspire the wearer to accomplish greatness and pursue their dreams. 


Tanzanite is a 6-7 on the Mohs scale of hardness and is durable enough for most jewelry applications. Because it can react to sudden temperature changes and abrade, Tanzanite should be removed from the setting before any jewelry work or repairs are done. It is recommended for earrings, pendants, and rings with a protective mounting..