While the mineral zoisite has been known for some time, gem-quality zoisite, called Tanzanite, wasn’t found until 1967, when a deposit was uncovered in Tanzania. This is still the only source for Tanzanite, one of the most recent additions to the gem world. Tanzanite gained almost immediate popularity both for its scarcity and its rich, blue-violet colour. It is often heat-treated to bring out a uniform colour. Tanzanite is noted for its trichroism (having 3 colours), an optical phenomenon – appearing three colours (blue, violet and burgundy/brown) depending on each stone’s crystal orientation. Tanzanite may also change appearance when viewed under alternate lighting.