Tanzanite is a dazzling gemstone known for its intense blue-violet hues and rarity. Belonging to the zoisite mineral group, it has captivated jewelers and collectors since its discovery. This remarkable gem isn’t just beautiful—it has a rich backstory, unique geological origins, and a growing role in the global gem market.
The Discovery of Tanzanite
In 1967, a Maasai tribesman stumbled upon brilliant blue crystals in the Merelani Hills near Arusha, Tanzania. These were quickly identified as a new variety of zoisite. Tiffany & Co. saw the gem’s potential and named it “Tanzanite,” introducing it to the world with a successful marketing campaign. Since then, Tanzanite has become one of the most desirable gemstones, known for its vibrant and shifting colors.
 |
Amazing Tanzanite el natural in pristine condition Photo Copyright ©️ Golden Hour Minerals |
Physical Characteristics
- Color: Tanzanite ranges from deep sapphire blue to violet and purple, depending on how it's viewed and the lighting. These colors come from trace amounts of vanadium and chromium.
- Clarity: High-quality tanzanite is usually transparent, though some stones contain inclusions.
- Crystal System: Tanzanite forms in the orthorhombic crystal system and typically appears as elongated, prismatic crystals.
- Hardness: With a Mohs hardness of 6.5 to 7, tanzanite is relatively durable but should be handled with care to avoid scratches.
 |
| Wow! Love this! of Course Tanzanite has Incredible Color From Arusha Region, Tanzania. Photo Copyright Mardani Fine Minerals |
Chemical Composition
Tanzanite is a calcium aluminum silicate with the formula Ca₂Al₃(SiO₄)(Si₂O₇)O(OH). Its unique color is due to trace amounts of vanadium and sometimes chromium. The exact chemical makeup can vary slightly depending on the geological conditions during its formation.
Mineralogy and Formation
Tanzanite forms under specific geological conditions in metamorphic rocks and is often found alongside garnet, diopside, and hornblende. Its formation is the result of intense heat and pressure deep within the Earth’s crust.
 |
| Spectacular gemmy lustrous trichroic Tanzanite Credit: MIM Museum / ©Fine Minerals International - James Elliot |
Refractive Index and Specific Gravity
- Refractive Index (RI): 1.691 to 1.700. This helps gemologists identify tanzanite and differentiate it from similar-looking stones.
- Specific Gravity (SG): 3.35 to 3.38. This measurement indicates the density of the gemstone.
Common Treatments
Tanzanite often undergoes enhancement treatments to improve its visual appeal:
- Heat Treatment: Almost all tanzanite is heat treated to remove brownish tones and enhance its vivid blue-violet color. This process is stable and widely accepted.
- Coating: Rare and temporary, coatings may enhance color but can wear off.
- Impregnation: Fractures may be filled with resin or glass to improve clarity.
- Clarity Enhancement: High-RI fluids may be used to make inclusions less visible.
- Radiation: Occasionally used to alter color, though not common in the tanzanite market.
Always purchase from trusted dealers and ask for certificates from reputable gemological labs to ensure full disclosure of treatments.
 |
| Photo Copyright @spirifer_minerals |
Market Value and Rarity
Tanzanite is a "single-source" gemstone—found only in a small mining area in Tanzania. This limited supply significantly boosts its rarity and value. Deep blue or richly violet stones with high clarity and excellent cuts command the highest prices.
 |
| 1) This typical paragenesis can be seen on this mineral specimen featuring a nice tanzanite crystal on calcite and graphite 2) A 6.56 carat tanzanite on a platinum and diamond ring by Tiffany & Co |
Tanzanite is more than just a beautiful stone—it’s a geological marvel with a captivating story. From its exclusive origin in Tanzania to its rare optical properties and global allure, tanzanite remains a favorite among gem enthusiasts and collectors. Whether worn as a stunning piece of jewelry or treasured in a collection, tanzanite continues to enchant with its one-of-a-kind charm.