Tanzanite Varieties: A Beginner's Guide to Blue Zoisite and Its Color Zones

Tanzanite, the blue-violet gemstone discovered only in the Merelani Hills of Tanzania, has captivated collectors and jewelry enthusiasts since its 1960s debut. Known scientifically as blue zoisite, this gem’s unique pleochroism — showing blue, violet, and burgundy hues depending on the viewing angle — makes it one of the most dynamic stones in the world. For a beginner, understanding tanzanite’s varieties is the key to appreciating its rarity and value. Unlike many gems that are classified primarily by color, tanzanite is graded by a combination of hue, tone, and saturation, with specific names for different color zones. This guide will walk you through the primary varieties of tanzanite, including the highly sought-after ‘violetish blue’ AAA grade, the ‘greenish blue’ less-common types, and the heat-treated versus natural color categories. We’ll also touch on related stones like iolite and sapphire, often confused with tanzanite, and explain how these varieties affect price, rarity, and desirability in the market.

What Makes Tanzanite Unique?

Tanzanite is a member of the zoisite mineral family, but its gem-quality form is exclusively found in a 7-by-2-kilometer area near Mount Kilimanjaro. Its most distinctive feature is pleochroism: in its rough state, trichroic tanzanite shows blue, violet, and red or burgundy colors. When cut correctly, a gem can display these colors simultaneously, creating a mesmerizing effect. The stone’s hardness (6.5–7 on Mohs scale) makes it suitable for jewelry with care. Natural tanzanite is typically brown or green before heat treatment, which transforms it into the popular blue-violet hues. Heated stones dominate the market; untreated examples are extremely rare and command premium prices, often called ‘natural color’ or ‘unheated’ tanzanite. This variety is prized by collectors for its earthy, olive-green to blue-green tones.

The Official Tanzanite Color Grading System

The Tanzanite Quality Scale, developed by the Tanzanite Foundation and refined by GIA, uses a five-category system: Type I (deep violetish blue), Type II (violet blue), Type III (blue to violet), Type IV (light blue or violet), and Type V (pale). However, trade terms like ‘AAA’ (top) or ‘A’ (lower) are more common. Within this, varieties are named by dominant hue and saturation. The most valuable tanzanite is ‘violetish blue’ with medium-to-medium-dark tone and strong saturation. But lesser-known varieties exist: ‘greenish blue’ tanzanite occurs when iron content is present; ‘orangey red’ rare stones occur due to natural trace elements. For beginners, it’s crucial to understand that color terms in tanzanite are not about distinct species but about gradations of the same mineral.

Common Tanzanite Varieties by Color

• Violetish Blue (AAA Grade): The classic—deep, rich, with equal parts blue and violet. Highest price per carat. Commonly heat-treated to achieve this.
• Blue-Violet: Slightly more blue than violet. Popular in engagement rings. Often called ‘Swiss blue’ in trade though not an official term.
• Violet: Strong violet hue with subtle blue. Less common; some prefer this for a more romantic look.
• Greenish Blue: Rare natural variety. Sells at a discount but prized by collectors for its earthy beauty.
• Brownish or ‘Champagne’: Usually untreated rough. Heat-treated to remove brown tones.

Heat-Treated vs. Natural Color Tanzanite

Over 95% of tanzanite on the market is heat-treated. The process involves heating rough tanzanite to about 480°C (896°F) to remove the brown or greenish component, revealing the desired blue-violet. This treatment is permanent and stable, accepted in the trade without disclosure only if standard. However, ‘natural color’ or ‘unheated’ tanzanite is a distinct variety that forms the upper echelon of rarity. These stones have a unique, often olive-green or teal-like appearance. They are less than 1% of production. A beginner should note that unheated tanzanite is seldom cut into calibrated sizes; most are custom. Price can be 2–5x higher than heat-treated equivalent.

Related Stones Often Confused with Tanzanite

Several gems share tanzanite’s color profile but have different properties. Knowing them helps avoid buying a different stone by mistake.

Iolite (Cordierite)

Iolite shows strong pleochroism, usually blue-violet to pale yellow, and is often called ‘water sapphire.’ It is less expensive, hardness 7–7.5, and more abundant. Iolite lacks tanzanite’s deep saturated red under incandescent light. From India or Sri Lanka, iolite is a budget-friendly alternative but has lower brilliance.

Sapphire

Blue sapphire (corundum) is harder (9) and has no pleochroism in the same way — it changes color under different lighting (like padparadscha). Top blue sapphire from Kashmir or Burma can be more expensive than tanzanite. Beginner confusion arises because both can be blue-violet. Key differentiators: sapphire has higher refractive index (brighter), no red flash, and different inclusions (silk, rutile).

Amethyst

Though typically purple, some amethyst from Zambia or Brazil can appear similar. Hardness 7, but pleochroism only weak. Amethyst is much cheaper. A gemologist can test via refractive index (tanzanite ~1.69–1.70 vs amethyst ~1.54–1.55).

Kyanite

Blue kyanite is often a lighter, more streaky blue. Hardness varies (4.5–5 along cleavage). Not typically used in rings due to fragility.

Benitoite

Rare blue barium titanium silicate from California. More expensive than tanzanite, with strong dispersion (fire). Hardness 6.5. Only known from one locale, but very different from tanzanite under magnification.

Rare and Unusual Tanzanite Varieties

Beyond the usual blue-violet, tanzanite can occur in rarer forms that intrigue collectors:

• Cat’s-eye Tanzanite: Contains parallel needle-like inclusions (rutile) causing a chatoyant band. Extremely rare, often from higher-grade material. Hard to find in larger sizes.
• Color-Change Tanzanite: Exhibits a distinct shift from blue under daylight to red-purple under incandescent. Not all tanzanite shows this strongly; true color-change stones are prized.
• Bicolor or Zone Color: Stones with two distinct color zones, usually blue and violet or green. Cut to feature the contrast. Unique artistic appeal.
• Fancy Cut Tanzanite: While not a variety of material, special cuts like ‘Tanzanite Star’ or ‘Radiant’ maximize color dispersion. Some are cut as cabochons.

Geographic Origin and Its Impact on Varieties

All gem-quality tanzanite comes from the Merelani Hills, near Arusha, Tanzania. The area is divided into four blocks (A–D), each producing different color ranges. Block D is known for deeper violetish blue. Block C yields lighter blues. Block B has highest productivity. This geographic exclusivity means tanzanite is a one-location gem, coining the phrase ‘one source, one origin’ used by marketers. Its scarcity drives its value. Unlike diamonds, no major alternative deposits exist, making each variety genuinely limited.

Buying Guide for Beginners: How to Choose a Tanzanite Variety

When buying tanzanite, match the variety to your budget and purpose. For everyday jewelry, heat-treated AAA or AA grade in blue-violet is most durable and affordable. For investment, seek natural color or color-change stones over 5 carats with certificates from GIA, AGS, or SSEF. Avoid stones with excessive inclusions (visible to naked eye). A beginning collector should prioritize color: strong uniform saturation with no dead zones. Pleochroism is a plus; ask the seller to rotate the stone under different lights. Carat weight: tanzanite is dense, so a 1-carat stone appears smaller than a 1-carat diamond. Shape: custom cuts can hide color variations. Always confirm origin (Tanzania) and treatment status. Prices range from $50 per carat for pale A grade to $600+ for top AAA violetish blue over 5 carats. Unheated stones can exceed $1,000 per carat.

Caring for Tanzanite

Tanzanite is not as hard as sapphire or diamond. Avoid ultrasonic cleaners and harsh chemicals. Clean with warm water and mild soap. Store separately to prevent scratches. Heat-treated tanzanite is stable but should not be exposed to strong heat (like torch). With care, a tanzanite gem can last a lifetime.

Conclusion

Tanzanite’s varieties — from the classic violetish blue to rare color-change and cat’s-eye — offer a spectrum of possibilities for gem lovers. Its single-source origin, unique pleochroism, and affordability relative to sapphire make it a sparkling choice for rings, earrings, and pendants. Beginners should focus on color grading and treatment, understanding that heat-treated is the norm and natural color a prize. By learning the nuances of tanzanite varieties, you can confidently select a stone that matches your taste, budget, and style. Whether you’re drawn to its blue depths or the rarity of a natural color zone, tanzanite remains a gem of remarkable beauty and character.