Tanzanite is the exquisite blue-purple variety of the mineral zoisite that is only found in one part of the world. Named for its limited geographic origin in Tanzania, tanzanite has quickly risen to popularity since its relatively recent discovery.
Zoisite had been around more than a century and a half before this rare blue variety was found in 1967. Trace amounts of vanadium, mixed with extreme heat, cause the blue-purple colour—which ranges from pale blue to intense ultramarine with violet undertones.
Due to pleochroism, tanzanite can display different colours when viewed from different angles. Stones must be cut properly to highlight the more attractive blue and violet hues and deemphasize the undesirable brown tones.
Most of the tanzanite on the market today is heat treated to minimize the brown colours found naturally and to enhance the blue shades that can rival sapphire.
Tanzanite is still only found on a few square miles of land in Tanzania, near majestic Mount Kilimanjaro. Its price and availability are directly tied to mines in this region, most of which are now slowing production significantly.
Tanzanite measures 6.5 to 7 on the Mohs scale of hardness—which is not nearly as hard as the sapphire it often substitutes. Given its vulnerability to scratch during daily wear and abrasion, tanzanite is better suited for earrings and pendants than rings.
Between its deep blue colour and its limited supply, tanzanite is treasured by many, even if your birthday is not in December.