• 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.