HISTORY and LORE
- First identified in the early 1960’s. Major deposits were discovered a few years later. Since then tanzanite has become a favorite colored gem around the world.
- Named for Tanzania, the East African nation where it was originally found.
- December birthstone and gem for the 24th wedding anniversary.
- Color: Light to dark purple, violet, or blue. Most expensive is deep pure blue. May show noticeable color shift – more bluish in daylight or fluorescent, and more purplish in incandescent light.
- Clarity: Often almost inclusion-free.
- Cut: Faceted in many shapes and styles.
- Carat Weight: Normally available in all jewelry sizes (up to 15 or 20 carats).
Virtually all tanzanite is heat treated to develop its color. A popular story says the possibility of treatment was recognized when a wildfire changed crystals lying on the ground from pale brown to rich blue. The treatment’s effects are normally permanent, and it creates no added special care requirements for gem owners.
- A variety of the mineral species zoisite. Zoisite more commonly occurs in translucent to opaque green or pink, and rarely in transparent green.
- Tanzanite has a complex chemical formula that includes calcium, aluminum, silicon, oxygen, and hydrogen. Color caused by trace amounts of vanadium.
Tanzanite needs gentle wear and care. Protective setting is recommended.
- Hardness: Moderate scratch resistance. Rates 6 to 7 on the Mohs Hardness Scale
- Toughness: Fair to low resistance to chipping and breaking because of cleavage (a tendency to split in certain directions due to crystal structure patterns).
- Stability: Sensitive to thermal shock. Rapid temperature change can cause breaks.
- Cleaning: Liquid cleaner, or detergent and water. NEVER USE AN ULTRASONIC.