Tanzanite has good one directional cleavage and uneven to conchoidal fracture. Tanzanite occurs in several habits, including prismatic, striated, and columnar. In one direction it is blue, in another, purple, and in a third direction it appears bronze. The smaller ones are usually more pale. Tanzanite looks different in different lighting situations.
Sunlight usually makes it look more purple.
Light bulbs and candlelight also bring out the purple and can make the grayish ones look brown. Fluorescent lights tend to bring out the blue more, as do overcast skies. Tanzanite has a molecular weight of 427.38 gm. back to top Localities Geologically, tanzanite is found in metamorphic rocks, pegmatite rocks, and hydrothermal veins. Geographically, tanzanite is found in only one place in the world, Merelani Hills of Tanzania around Mount Kilimanjaro. Specifically, in Merereani is in the Arusha province, which is located in the Simanjiro District of Northern Tanzania.