Overview
About Tanzanite
Found in just one place on earth, tanzanite is a relatively recent discovery. Tiffany & Co named this blue-violet variety of zoisite in honor of Tanzania, where it was first unearthed in 1967. Because the crystals show different colors depending on the viewing direction, cutters can fashion gems with a range of color from violetish blue to bluish violet depending on how much weight they want to retain from the rough.
Birthstones & Anniversaries
Tanzanite is a birthstone for December, along with zircon, turquoise, and blue topaz. Tanzanite is also the gem for a 24th anniversary.
Merelani
Tanzanite has only one source: the hills of Merelani in northern Tanzania.
1967
Masai tribesman Ali Juuyawatu is credited with finding the first tanzanite crystal.
Pleochroic
Tilt tanzanite and you’ll see three distinct colors in three crystal directions.
Facts
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Mineral:
Zoisite
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Chemistry:
Ca2Al3(SiO4)3(OH)
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Color:
Violet blue to bluish violet to violet purple
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Refractive Index:
1.691 to 1.700
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Birefringence:
0.008 to 0.013
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Specific Gravity:
3.35
- Mohs Hardness: 6 to 7
Treatments
There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.
Learn MoreSynthetics
Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.
Learn MoreImitations
Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.
Learn More
Why We Love This Gemstone
Pleochroic
Tanzanite is pleochroic, showing three different colors when viewed from different directions.
One Place on Earth
Commercially mined in only one place, tanzanite is rarer than diamond.
Rich Blue
Tanzanite's rich blue-to-violet hues can be exceptionally beautiful.
Quality Factors
Assessment of the following characteristics determines tanzanite’s value.
Color
Deep saturated violet blue or blue violet are the most valuable tanzanite colors. Paler hues are more commonly found.
Clarity
Eye-visible inclusions decrease the value of tanzanite, particularly in lighter colored stones.
Cut
Tanzanite is available in a wide range of shapes but cushion and oval cuts are most common.
Carat Weight
Tanzanite color is less saturated in smaller sizes. Gems must be above five carats in size to have fine color.
Tanzanite Quality Factors: The Comprehensive Guide
Research
Explore sources, gemological research, and the role of gems in history.
Merelaniite Inclusions in Tanzanite
Augusto Castillo, Tyler Smith, and John A. Jaszczak , Aug 9, 2018 Read Article
Recommended Reading
Emerald & Tanzanite Buying Guide
Renée Newman
Gems of the World
Cally Oldershaw
