Back to gem encyclopedia


Poised between lush blue, vibrant violet, and rich purple, exotic tanzanite is found in only one place on earth, near majestic Mount Kilimanjaro.

Responsive image
Unique Hues

Unique violet-to-blue hues

Responsive image
Pure Blue

Tanzanite's rich hues rival sapphire's beauty.

Responsive image

Tanzanite's color blends blue hue and violet pleochroic hues.

Responsive image
Responsive image
Tanzanian Beauty

This beautiful Merelani tanzanite crystal measures 4 x 2.9 cm.

Responsive image
Pleochroic Colors

This crystal shows strong blue and brownish green pleochroic colors.

Responsive image

This crystal shows traces of the rock where it grew on its base.

Responsive image


About Tanzanite

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.

Tanzanite Description

Tanzanite History and Lore

Tanzanite Journey

Birthstones & Anniversaries

Tanzanite is a birthstone for December, along with zircon, turquoise, and blue topaz. Tanzanite is also the gem for a 24th anniversary.


Tanzanite has only one source: the hills of Merelani in northern Tanzania.


Masai tribesman Ali Juuyawatu is credited with finding the first tanzanite crystal.


Tilt tanzanite and you’ll see three distinct colors in three crystal directions.


  • Mineral: Zoisite
  • Chemistry: Ca2Al3(SiO4)3(OH)
  • Color: Violet blue to bluish violet to violet purple
  • Refractive Index: 1.691 to 1.700
  • Birefringence: 0.008 to 0.013
  • Specific Gravity: 3.35
  • Mohs Hardness: 6 to 7


There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.

Learn More


Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.

Learn More


Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.

Learn More
gem love

Why We Love This Gemstone


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.


quality factors

Deep saturated violet blue or blue violet are the most valuable tanzanite colors. Paler hues are more commonly found.


quality factors

Eye-visible inclusions decrease the value of tanzanite, particularly in lighter colored stones.


quality factors

Tanzanite is available in a wide range of shapes but cushion and oval cuts are most common.

Carat Weight

quality factors

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


Explore sources, gemological research, and the role of gems in history.

Large, fine-color tanzanites

Natural-Color Tanzanite and Yellow Sapphire – Tucson 2014

Duncan Pay , Apr 30, 2014 Read Article
Titanium-coated tanzanite

Titanium-Coated Tanzanite

Amy Cooper and Nathan Renfro , Apr 30, 2014 Read Article
Merelaniite whisker inclusions in tanzanite.

Merelaniite Inclusions in Tanzanite

Augusto Castillo, Tyler Smith, and John A. Jaszczak , Aug 9, 2018 Read Article
An iridescent cleavage in tanzanite

Iridescent Inclusion in Tanzanite

Danny Sanchez , Nov 7, 2016 Read Article