What is tanzanite?
By Jared James · Last updated 21 May 2026
Definition
Tanzanite is a blue-violet variety of the mineral zoisite, found only in a small area near Mount Kilimanjaro in northern Tanzania, which makes it roughly a thousand times rarer than diamond. Its colour ranges from a light periwinkle to an intense, deep blue-violet, and the stone is naturally trichroic, meaning it shows different hues of blue, violet and burgundy depending on the angle. Most tanzanite is heat-treated to enhance its blue tones. It was added as a December birthstone in 2002.
Frequently asked questions
- Why is tanzanite so expensive?
- Tanzanite comes from a single small mining area in Tanzania, so supply is genuinely limited and the mine is expected to be exhausted within decades. That geographic exclusivity, combined with its striking colour, drives prices considerably higher than most semi-precious stones of comparable size.
- Is tanzanite good for an engagement ring?
- Tanzanite is beautiful but rates only 6 to 7 on the Mohs hardness scale, which makes it softer and more prone to chipping than sapphire or diamond. It can work well in an engagement ring if the setting protects the stone, such as a bezel or halo, and if the wearer is careful with it, but it needs more attention than a harder gem.
- What is tanzanite's birthstone month?
- Tanzanite is one of three December birthstones, added to the list in 2002 alongside turquoise and blue topaz. It is a popular modern choice for December birthdays because of its rich, blue-violet colour and its relative rarity compared with the other December options.
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