Did you know your tanzanite received a heat treatment? Some people are mortified to learn that many of the colored gemstones of today weren't pulled from the earth with that hue, but have been heat treated. The heat reduces and improves inclusions, and can also be used to modify the color of the stone. It can become lighter, darker, or even change colors completely. Tanzanite in its final form is a blueish/purple. Some tanzanite, when pulled from the ground is actually brown, but a carefully controlled heat treatment brings out the color- heat treatment basically continues the process started in the earth, by rearranging its molecular structure. This is done in a furnace near 500-600 degrees Celsius, and requires careful control- too much heat and the tanzanite can be ruined. Almost every tanzanite stone has been heat treated, so it does not affect the price. Also all finished gems are assumed to be heat treated.