A Guide to Tanzanite
Found in One Place on Earth • December Birthstone • Rarer Than Diamond
Tanzanite is one of the most remarkable gemstones in the world, and one of the rarest. Found in only a single location on earth, a few square kilometres of the Merelani Hills near Mount Kilimanjaro in Tanzania, it is estimated to be a thousand times rarer than diamond. Its extraordinary blue-violet colour, which shifts and deepens depending on the light, has captivated collectors and jewellery lovers since its discovery in 1967. As the December birthstone and a stone of genuine geological scarcity, tanzanite carries both beauty and significance in equal measure.
Where is Tanzanite Found?
Tanzanite was discovered in 1967 by a prospector named Manuel de Souza in the Merelani Hills near Mount Kilimanjaro, Tanzania. It was initially mistaken for a sapphire before being identified as an entirely new gemstone variety. Tiffany and Co of New York introduced it to the world under the name tanzanite, after the country of its origin.
The entire known deposit covers only around 4 square kilometres, making tanzanite one of the most geographically restricted gemstones in existence. Geologists believe the unique combination of geological conditions required to form tanzanite occurred just once in the earth's history, which is why it exists in only this single location. Current estimates suggest the deposits could be depleted within a matter of decades, which adds a further sense of urgency and significance to owning a tanzanite piece today.
What Makes Tanzanite Exceptional?
Tanzanite possesses several qualities that set it apart from every other gemstone. Understanding these characteristics helps explain why it is so highly valued by collectors and jewellery lovers alike.
1
Trichroism
Tanzanite is the only gemstone known to be trichroic, meaning it simultaneously displays three distinct colours: blue, violet and burgundy red. The colour seen depends on the angle from which the stone is viewed and the quality of the light. This optical phenomenon is unique in the gem world and gives tanzanite a living, shifting quality that no other stone can replicate.
2
Colour
In daylight, the finest tanzanite displays a rich ultramarine to sapphire blue. In incandescent or artificial light, it shifts towards a deeper amethyst violet. The most valuable stones show a vivid, saturated blue-violet with strong colour across both lighting conditions. Lighter or more grey tones are less prized.
3
Cut
The cut of tanzanite is critical to how its colour and trichroism are displayed. Tanzanite is most commonly cut in cushion, oval and emerald shapes, which best enhance its depth of colour. A skilled cutter will orient the stone to show the most desirable blue-violet face up, maximising the stone's visual impact.
4
Rarity
With deposits confined to a single location and estimated to be depleted within decades, tanzanite is a genuinely finite resource. This scarcity is not a marketing narrative but a geological reality, and it is one of the key reasons why tanzanite continues to appreciate in desirability among collectors and investors.
Heat Treatment and Natural Tanzanite
The vast majority of tanzanite on the market today has been heat-treated to enhance its blue-violet colour and remove the brownish hues that are present in rough, untreated material. This process is stable, widely accepted throughout the gemstone industry and considered standard practice for tanzanite.
Untreated tanzanite is rare and typically displays a less intense colour in its natural state. When untreated stones do show strong colour naturally, they are considered particularly remarkable and can command a premium. At Cheshires, we are always transparent about treatment status and happy to discuss the provenance of any stone in our collection.
Tanzanite in an Engagement Ring
Tanzanite scores 6 to 7 on the Mohs scale of hardness, which means it requires more careful consideration for use in an engagement ring than a diamond, sapphire or ruby. It is susceptible to chips and surface scratches with daily wear over time.
That said, with the right setting, tanzanite can absolutely be worn in an engagement ring. A bezel setting or a well-designed halo provides meaningful protection to the stone and allows its colour to be the focus. With thoughtful care, a tanzanite engagement ring can be a deeply personal and strikingly beautiful choice.
Quick Facts
Birthstone December
Hardness 6 to 7 Mohs
Source Tanzania only
Discovered 1967
Special Feature Trichroic: blue, violet and red
Rarity 1,000 times rarer than diamond
Why Choose Tanzanite Jewellery?
Tanzanite offers something that very few gemstones can: the combination of extraordinary beauty, genuine rarity and a story that is unlike any other stone. It exists in one place on earth, formed once in geological history, and the deposits that remain are finite. Owning a fine tanzanite is, in a very real sense, owning a piece of something that cannot be replaced.
Its shifting blue-violet colour is unlike anything else in fine jewellery. No two stones are quite the same, and the way tanzanite responds to different light conditions gives it a warmth and depth that rewards close attention. Whether set as a statement pendant, a pair of earrings or a striking ring, tanzanite makes its presence felt with quiet confidence.
As the December birthstone, it also carries a personal significance for those born in that month, and its rarity makes it a meaningful and considered gift for anyone who appreciates the extraordinary.
Discover Our Tanzanite Collection
At Cheshires, each tanzanite is hand-selected for depth of colour, clarity and cut. Visit us in store to see our curated selection, or book a personal appointment with our gemstone specialists.
