The Zoisite Mineral Family: Tanzanite, Thulite, and Anyolite

The zoisite mineral family contains some of the most commercially significant and visually diverse gems in the colored stone world. Tanzanite—one of the most popular colored gems of the last half-century—is the star of the family. But zoisite also includes thulite (pink), anyolite (green zoisite with ruby), and the rare chrome zoisite that gives anyolite its vivid green matrix. Understanding the full family enriches both sales knowledge and collection depth.

Tanzanite — Blue-Violet Zoisite

Tanzanite is the trade name for blue-violet zoisite from a single deposit near Arusha, Tanzania. Discovered in 1967 and marketed exclusively by Tiffany & Co. (who coined the name), tanzanite rapidly became one of the world’s most popular colored gems. Its vivid blue-violet color—ranging from pale lilac to deep royal blue-violet—is unmatched in nature. Tanzanite is strongly trichroic, displaying blue, violet, and burgundy in different crystal directions; heating aligns the pleochroic colors into the familiar blue-violet.

Tanzanite Quality Factors

Color: Deep, saturated blue-violet is most valued; stones that lean more blue command higher prices than those leaning purple-gray

Tone: Medium to dark tones are preferred; very light or very dark stones trade at discounts

Clarity: Tanzanite is typically eye-clean; major inclusions are rare but reduce value significantly

Cut: Well-proportioned cuts maximize the blue-violet color; shallow cuts appear pale and lifeless

Size: The color deepens in larger stones; stones under 5 carats are often lighter in tone

Heat treatment: Standard and universal; nearly all tanzanite on the market is heated; untreated tanzanite is not a premium category

Tanzanite Market Considerations

Tanzanite comes from a single source—when the Merelani Hills mine is exhausted, there will be no more tanzanite. This finite supply has supported long-term price appreciation for fine quality. The Tanzanian government has periodically restricted rough exports to encourage local cutting, affecting supply. Political and mining stability in Tanzania remains a factor in long-term supply forecasts.

Thulite — Pink Zoisite

Thulite is manganese-bearing pink to rose-red zoisite. First found in Norway (named after the mythical land of Thule), it is also found in North Carolina and other locations. Thulite is typically opaque to translucent and used for carvings, cabochons, and beads rather than faceted gems. Its warm pink color makes it a popular carving material and an affordable alternative for pink gem seekers.

Anyolite — Ruby in Zoisite

Anyolite is a natural combination of green zoisite matrix with embedded ruby crystals and black hornblende inclusions. Found in Tanzania (near the Longido district), it produces dramatic carvings and decorative objects—the vivid red of the ruby against the bright green zoisite is visually striking. Anyolite is not typically faceted; its value lies in the decorative combination rather than transparency or optical properties.

Care for Zoisite Gems

Tanzanite has a Mohs hardness of 6.5 and perfect cleavage in one direction, making it more fragile than corundum or beryl. Protective settings (bezel or halo) are recommended, especially for rings. Ultrasonic cleaning is generally safe for untreated tanzanite, but steam cleaning and sudden temperature changes should be avoided. The softer nature of tanzanite means it is best suited to earrings, pendants, and occasional-wear rings rather than everyday pieces.