One of the best kept secrets of the tanzanite trade is the exceptionally rare occurrence of fancy, colored tanzanite, like natural green tanzanite. Tanzanite's incredible rarity and beauty have skyrocketed it to the highest ranks of the gemstone kingdom.
Green Tanzanite hit the market about 20 years ago and is similar in color to chrome tourmaline. Like other tanzanite, this gem is famous for having multidimensional color and being exceptionally brilliant. It exhibits a strong amount of pleochroism, meaning that it appears different colors when viewed from different angles. Green tanzanite has red-violet and blue undertones, with a green base color. Tanzanite is a blue-violet variety of the mineral zoisite. Green and pink varieties are considered the rarest. These colors are called fancy tanzanite, although technically this gem is a green zoisite. Tanzanite has a single source in Tanzania. Recently, deeper mining practices have unearthed extremely rare pink, orange, yellow and green varieties. Green tanzanite is completely natural and accounts for approximately one percent of all tanzanite.
The world's only known source of tanzanite was discovered deep in the foothills of Mount Kilimanjaro in Tanzania, East Africa in 1967. Geologists say the chemical environment required to form this gem is so unique that the probability of discovering another tanzanite deposit is less than one in a million. The quality and quantity of gem deposits vary and the production of sellable rough is not consistent at all depths. If other deposits are not located (and that seems unlikely), geologists estimate the original supply of tanzanite will dry up within 30 years.