Tanzanite Treatments, Imitations and Synthetics
Tanzanite is often heat treated to improve clarity. Unheated stones of good clarity will be worth more than heated stones of the same clarity.
Tanzanite is becoming increasingly simulated in recent years in response to the apparent “drying up” of natural “earth mined” tanzanite. Most sellers will disclose whether or not the stones are imitation, but it is always a good idea to ask. If you see perfectly colored, perfectly clear tanzanite gemstones over 1 carat that are being offered at a low price (less than $100), you can suspect already that they are simulated.Sometimes finely colored iolite is used as a substitute or imitation for tanzanite. Iolite has the same pleochroic (showing two colors) affect as tanzanite, but is a natural gemstone in its own right.
A synthetic tanzanite would be a gemstone that is a real tanzanite (with the same chemical and minerological composition, same optical and physical properties). The only difference would be that a synthetic tanzanite is man made in a labratory. Synthesizing gemstones is usually an expensive procedure: it rarely makes economic sense. In the case of tanzanite, there is no synthesis occuring that we know of. This means that if you see “synthetic tanzanite” available for sale, it is probably another synthetic mineral (such as corundum or garnet)
Tanzanite gemstones are sensitive to ultrasound. This means that ultrasonic gem cleaners that are found is some jewelry shops should never be used on tanzanite, since it can cause irreparable damage.