Tanzanite

Tanzanite was discovered in 1967 when Maasai tribesman Manuel d'Souza stumbled upon blue crystals near Merelani at the foot of Kilimanjaro in Tanzania. D'Souza registered four mining claims; by 1969 the mineral was identified as a transparent variety of zoisite — a mineral until then known only as an opaque stone without gem properties.

Tiffany & Co. named the stone "tanzanite" in 1968 — a name evoking the mystery and exoticism of Africa. Tanzania nationalized the mine in 1971, causing confusion and a drop in production. The late 1980s brought oversupply and falling prices; in 1998 floods killed 100+ miners trapped underground. Following false reports of Al-Qaeda financing in 2002, tanzanite commerce halted for a year; investigation revealed the allegations were baseless, and in 2003 "Tanzanite Protocols" were established for traceability.

Trichroism is tanzanite's defining property: viewed from three crystal axes, the stone shows three different colors — blue, violet, and burgundy-red. The cutter determines which of the three tones will dominate the finished stone. The most prestigious color is intense blue-violet with visible reddish flash ("velvet blue"). Lower quality stones are pale violet or gray.

Unique geology: Tanzanite forms only in precisely defined geochemical conditions — a combination of arid metamorphic rocks, specific minerals, and geographic location. Geologists assess that this geological combination would occur only once on Earth — meaning the deposit will never be replicated or discovered elsewhere. The mine is estimated to have 10–30 years of reserves remaining.

Rarity and future: Tanzanite is 1,000× rarer than diamond. Since the mine is the world's only source with limited reserves, many experts predict dramatic price increases once reserves are exhausted. Some call it a "generational stone."

Tanzanite and blue-violet color: Tanzanite is often confused with blue sapphire or aquamarine, but it has a unique blue-violet tone found in no other gemstone. Under incandescent light, violet overtones become more pronounced.

Tanzanite originates exclusively from an area of 30 km² near Merelani in Tanzania — the only known deposit on Earth. Because the source is geographically limited, tanzanite is per GIA considered rarer than diamond. The mine is divided into sectors; TGME (Tanzanite One) controls the largest commercial sector. Some geologists estimate that at the current rate of extraction, existing deposits will be exhausted within 20–30 years.

Tanzanite is relatively new on the jewelry market: fewer than 60 years have passed since its discovery in 1967 before it became one of the five most popular colored gems in the world. 95% of blue tanzanites are heat treated — naturally blue stones are a rare natural occurrence.

Tanzanite is trichroic: when viewed from different angles it displays blue, violet, and reddish color simultaneously. The cutter must carefully orient the stone to determine which color will dominate face-up — blue is more sought-after, but orienting for violet wastes less material.

Per GIA, tanzanite is the only gemstone whose value is based on possession of a single exclusive deposit. If a new deposit were found anywhere in the world, it would significantly impact the market price — unlike diamond, which has sources on every continent.

Raw tanzanite is typically brownish-yellow in color. The blue color for which it is known develops only after heat treatment at 500–600°C. Naturally blue tanzanites have existed but are exceptionally rare.