What Is Tanzanite?
Tanzanite is the blue-violet variety of the mineral zoisite (calcium aluminum silicate, Ca₂Al₃(SiO₄)₃(OH)), colored by trace amounts of vanadium. It was discovered in 1967 near the Merelani Hills of northern Tanzania — and has been found nowhere else on earth.
This single-source origin is the foundation of tanzanite's rarity and value. Unlike diamonds (found on multiple continents), rubies (found across Asia and Africa), or sapphires (found worldwide), tanzanite exists in one 8-square-mile deposit at the foot of Mount Kilimanjaro. When that deposit is exhausted — estimated within the next 20–30 years — no new tanzanite will ever be mined.
Tiffany & Co. named the stone "tanzanite" in 1968 and launched it to the world market. It has since become one of the most popular colored gemstones globally, consistently ranking among the top three colored gemstones sold worldwide alongside sapphire and emerald.
Geological Formation
Tanzanite's formation is geologically extraordinary. It requires a very specific combination of conditions that occurred only once, in one place:
- The Mozambique Orogenic Belt — a 500-million-year-old mountain-building event that created the metamorphic rocks of the Merelani Hills
- Specific pressure and temperature conditions during metamorphism that allowed vanadium-bearing zoisite to crystallize
- Subsequent tectonic activity that brought the tanzanite-bearing rocks to the surface
Geologists estimate the probability of tanzanite forming elsewhere on earth at approximately one in a million. The deposit was discovered by a Maasai tribesman named Ali Juuyawatu in 1967, who showed the blue crystals to prospector Manuel de Souza, who initially mistook them for sapphires.
Physical Properties
- Chemical formula: Ca₂Al₃(SiO₄)₃(OH) with vanadium
- Crystal system: Orthorhombic
- Hardness: Mohs 6–6.5 — softer than sapphire; requires protective settings for rings
- Cleavage: Perfect in one direction — vulnerable to sharp impacts
- Specific gravity: 3.35
- Refractive index: 1.691–1.700
- Pleochroism: Strong trichroism — appears blue, violet, and burgundy from different angles
The Defining Characteristic: Trichroism
Tanzanite's most remarkable optical property is its strong trichroism — it displays three different colors when viewed from three different crystallographic axes: blue, violet, and burgundy/red-brown. This means the color you see depends on the angle from which you view the stone.
Cutters orient tanzanite to maximize the blue-violet face-up color — the most commercially desirable. Stones cut with the burgundy axis face-up are less valuable but show a completely different, equally beautiful color.
Color Grading: The Most Important Quality Factor
Color is the primary determinant of tanzanite value. The Tanzanite Foundation has developed a standardized grading system:
Hue
The finest tanzanite is a pure, vivid blue-violet — sometimes described as "electric blue" or "cornflower blue with violet overtones." The ideal hue is approximately 75% blue and 25% violet, creating a rich, complex color that shifts between blue and purple depending on lighting conditions.
- Top grade (AAA): Vivid blue-violet with strong saturation. The color appears to glow from within.
- High grade (AA): Strong blue-violet, slightly less saturated than AAA.
- Commercial grade (A): Medium blue-violet, lighter saturation.
- Lower grades: Pale lavender to pale blue. Still genuine tanzanite but significantly less valuable.
Saturation
Saturation refers to the intensity of the color. Highly saturated tanzanite appears rich and vivid; low saturation appears pale and washed out. Saturation is the single most important factor in tanzanite value after hue.
Tone
Tone refers to the lightness or darkness of the color. The ideal tone is medium to medium-dark — light enough to show brilliance, dark enough to show rich color. Very dark stones lose brilliance; very light stones appear pale.
Clarity
Tanzanite is a Type I gemstone in the GIA clarity classification — meaning it is expected to be eye-clean (no inclusions visible to the naked eye) in high-quality material. Inclusions significantly reduce value.
- Eye-clean: No inclusions visible without magnification. Standard for quality tanzanite.
- Slightly included: Minor inclusions visible under magnification but not to the naked eye. Acceptable at lower price points.
- Included: Inclusions visible to the naked eye. Significantly reduced value.
Cut
Tanzanite's trichroism means cut orientation is critical — the cutter must orient the stone to show the most desirable blue-violet face-up. Well-cut tanzanite shows excellent brilliance and even color distribution. Poorly cut stones may show windowing (a washed-out area in the center) or extinction (dark areas).
Common cuts include oval, cushion, pear, and round brilliant. Oval and cushion cuts are most common for tanzanite as they preserve the most weight from the rough crystal.
Heat Treatment: The Industry Standard
Virtually all tanzanite sold commercially is heat-treated. Raw tanzanite is typically brownish-burgundy; heat treatment at approximately 600°C converts the stone to its characteristic blue-violet color by altering the vanadium oxidation state. This treatment is permanent, stable, and universally accepted in the trade.
Untreated tanzanite (showing natural blue-violet without heat treatment) is extremely rare and commands significant premiums among collectors.
Investment Considerations
Tanzanite has attracted significant investment interest due to its single-source rarity and finite supply. Key considerations:
- Supply is finite: The Merelani deposit is estimated to be exhausted within 20–30 years. No new tanzanite deposits have been found despite extensive exploration.
- Demand is growing: Particularly in Asian markets, where tanzanite has seen significant price appreciation.
- Quality matters enormously: Investment-grade tanzanite is AAA color, eye-clean, well-cut, and 5 carats or larger. Lower quality material does not appreciate at the same rate.
- Certification is essential: Investment-grade tanzanite should be accompanied by a certificate from a recognized gemological laboratory (GIA, AGL, or Gübelin).
For the complete investment guide, see: Why is Tanzanite So Rare? An Investment Guide for Gemstone Buyers.
Metaphysical Properties
The following reflects spiritual traditions. See our editorial policy.
Tanzanite is associated with the third eye and crown chakras — its blue-violet color spanning both energy centers. In crystal traditions, it is said to enhance intuition, support spiritual development, facilitate communication with higher guidance, and assist in accessing deeper states of meditation. Its rarity is said to amplify its energetic potency.
Shop Tanzanite at Brie & Marie
Browse our Tanzanite collection — loose stones and jewelry in sterling silver and gold, with color grade, clarity, and carat weight disclosed on every listing. Related guides: How to Choose High-Grade Tanzanite Rings and Pendants • Why is Tanzanite So Rare?
