Tanzanite | Heated Blue-Purple Variety of Zoisite

Tanzanite — The Jewel of the Merelani Hills

In its finest form, tanzanite displays an intense blue-violet glow that no other gemstone can truly replicate. Discovered in the late 1960s, it quickly gained fame for rivaling — and in some cases outshining — the beauty of blue and purple sapphire. In 1967, Tiffany & Co. attempted to market tanzanite as a sapphire alternative; while that strategy fell flat, tanzanite soon proved it could stand on its own as one of the most coveted modern gemstones.

A variety of the mineral zoisite (Ca₂Al₃(SiO₄)₃(OH)), tanzanite is celebrated for its trichroism — the ability to display three distinct colors when viewed from different directions: blue, violet, and a bronze or brownish tone. The interplay of these hues creates tanzanite’s unmistakable charm.

Color and Formation

Tanzanite’s signature blues and purples come from trace amounts of vanadium in the crystal structure. In its natural state, zoisite is often brownish; a gentle heat treatment — replicating natural metamorphic conditions — removes the brown and reveals a vibrant blue or violet.

• Small stones often display soft, lavender tones.

• Larger stones can reach exceptional saturation, with pure blues among the most prized.

• Pure blue cuts require removing more rough material, as the purple axis tends to dominate in natural crystals.

Durability and Care

• Mohs hardness: 6–7 — moderately hard, but more susceptible to scratches than sapphire.

• Best use: Earrings, pendants, or rings with protective settings.

• Avoid: Ultrasonic cleaners, sudden temperature changes, or hard impacts.

Cultural and Metaphysical Significance

• Birthstone: Added as a December birthstone in 2002.

• Zodiac: No historical astrological link, given its recent discovery.

• Lore: Believed to bring calm, clarity, and heightened spiritual awareness, making it a popular stone for meditation.

Geographic Origin

All known tanzanite comes from a single source: the Merelani Hills of northern Tanzania, near Mount Kilimanjaro. While the deposit has yielded thousands of kilos of rough since its discovery, its geographic exclusivity adds to the gemstone’s allure. Mining continues today, making tanzanite widely available, though its single-origin status often prompts discussion about long-term supply.