There is only one place in the world where tanzanite is commercially mined.
The Merelani Hills of northern Tanzania, near Mount Kilimanjaro, are the sole known commercial source of this rare blue-violet gemstone. Unlike gemstones found across several countries and geological deposits, tanzanite's occurrence is confined to this very small area; an important part of its rarity.
For Steffi Widmer, FGA, Founder of Stefania’s Stones, understanding a gemstone means looking beyond its finished appearance to its geology, origin and individual characteristics.
During a recent trip to Tanzania, Steffi had the opportunity to visit the tanzanite mining area and source stones first-hand, gaining a closer understanding of where these gemstones begin their journey.
A Rare Gemstone Defined by Its Origin
Tanzanite is the blue-to-violet variety of the mineral zoisite. Its known commercial source is restricted to the Merelani Hills, with Mount Kilimanjaro rising just north of the mining area.
This highly restricted geological occurrence is what makes tanzanite particularly rare. The deposit itself is a finite natural resource, and mining at Merelani can take place at considerable depths with documented operations reaching more than 1,000 metres underground.
As mining progresses deeper underground, extraction naturally becomes more complex. Ultimately, the future availability of economically recoverable gem-quality material is constrained by both the geology of the deposit and the practical realities of mining it.
The Blue-Violet Character of Tanzanite
One of tanzanite's defining gemmological characteristics is pleochroism; the ability to display different colours when viewed along different crystallographic directions.
Unheated tanzanite can exhibit blue, violet and yellow-green to brownish tones. Most tanzanite on the market is routinely heat treated, which reduces the yellow-green or brownish component and develops the blue-to-violet appearance for which the gemstone is best known. This is a widely accepted treatment within the gemstone trade.
Colour is also influenced by how the rough is oriented during cutting. A cutter may make different decisions depending on whether the aim is to emphasise blue or violet, while also considering the proportions and weight retained from the original rough.
For a gemmologist, understanding these characteristics is part of selecting a tanzanite alongside its saturation, clarity, cut and overall visual character.
Selecting Tanzanite: One Stone or Many
Selecting one centre stone is very different from selecting several coloured gemstones that need to work together.
The Tanzanite Gallery Ring from ORIGINE features a 2.9-carat cushion-cut tanzanite personally sourced by Steffi in Tanzania. It was selected for its vivid saturation, excellent clarity, unique cut and distinctive balance of blue and violet.
Its proportions and optical character became the starting point for the design, with the gemstone held within a structured gallery setting that keeps the tanzanite at the centre of the piece.
For the Tanzanite Halo Hoop Earrings and Tanzanite Rhythm Ring, the challenge was different. Multiple round tanzanites needed to be carefully selected and matched for colour, tone and brilliance.
Natural coloured gemstones will always carry subtle differences. The aim is not necessarily to make them appear identical, but to find stones whose individual characteristics work together as a balanced composition.
From Tanzania to ORIGINE
Some of the tanzanites sourced during Steffi's trip to Tanzania have since become part of ORIGINE, the gemstone-led collection by Stefania’s Stones × MÉTIER.
At the heart of ORIGINE is a simple philosophy:
The stone leads. The design follows.
Explore ORIGINE’s Tanzanite Collection
Discover the tanzanites personally sourced directly in Tanzania by Stefania’s Stones and transformed into one-of-a-kind designs through the ORIGINE collaboration with MÉTIER.
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