Tanzanite is the blue to violet variety of the mineral zoisite. It is one of the few gemstones with a single source: every genuine tanzanite comes from a small area of the Merelani Hills in northern Tanzania, in the shadow of Mount Kilimanjaro. It was found there in 1967 and named the following year by Tiffany & Co.
At a glance it can pass for a fine blue sapphire, and that is often how people first meet it. Look closer and it shows a violet cast that sapphire does not, along with a soft internal glow. It is also, in the right light, quietly theatrical: turn the stone and it shifts between blue, violet and a deeper burgundy.
What Is Tanzanite?
Zoisite is a common enough mineral, but the blue-violet form is not. Its colour comes from traces of vanadium in the crystal. Most rough leaves the ground looking brown or khaki, and a controlled heat, usually around 550 degrees Celsius, shifts the vanadium and brings out the blue and violet. The colour that results is permanent.
Tanzanite is strongly pleochroic, which means it shows different colours down different axes of the crystal: blue, violet and brownish-bronze. A cutter has to decide which colour to favour, usually the blue-violet, which is why a well cut tanzanite is worth paying for.
Heated or Unheated?
Almost all tanzanite on the market has been heated. It is a standard, stable treatment, not a flaw, and it is what gives most tanzanite its blue. Unheated tanzanite is genuinely uncommon. Some of it is naturally blue, changed underground by the heat of the earth long ago; more often the unheated stones are a softer greyish-violet, which some people prefer for exactly that reason. Our unheated tanzanite engagement ring page covers that look in detail.
Choosing a Tanzanite
Colour is the main thing. The most valued stones are a deep, saturated violetish-blue with no grey or brown showing. Paler stones are common and much more affordable. Clarity is rarely a problem: most tanzanite is eye-clean and a good number are loupe-clean. Size is not the constraint it is with many coloured stones, since the rough often comes out large, so pendant and statement sizes are easier to find than with sapphire or ruby.
Supply is the real question. The Merelani deposit is small and the Tanzanian government has tightened control of exports in recent years, so good material has become harder to source and prices for the better colours have risen. It is a stone chosen for its colour and its story rather than as an investment.
Living With Tanzanite
Tanzanite is 6 to 7 on the Mohs scale, softer than sapphire, and it has one direction of easy cleavage, so a sharp knock can chip it. It also dislikes sudden temperature change and ultrasonic cleaners. None of that rules it out for a ring, but it does mean a protective setting such as a bezel or a low halo, and taking it off for sport or heavy work. As a pendant or earrings it needs far less thought. Tanzanite is the December birthstone, so it doubles as a birthstone piece.
Tanzanite Engagement Rings
One of our own pieces is a 4.39 carat cushion unheated tanzanite in 18K white gold, held in a round diamond halo with a zig-zag band. The diamonds frame the stone and keep the focus on its colour. For the full range of tanzanite engagement designs, heated and unheated, see our unheated tanzanite engagement ring page.
Tanzanite Pendants
Because tanzanite is on the soft side, a pendant is often the easiest way to wear a larger stone. One commission set a pear-shaped tanzanite below a diamond-framed ribbon, made as a Christmas gift and matched to the recipient as a December birthstone. Another set an unheated tanzanite horizontally in a diamond halo on a champagne gold chain, a plainer, more modern take.
Tanzanite Wedding Rings
For one couple we made a round tanzanite proposal ring in a six-prong rose gold setting with a marquise diamond on the shoulder, then a matching stack: the woman’s band carried pink spinel to pick up a warm contrast, and the man’s was rose gold with a brushed matt finish and a strip of black-plated gold down the centre.
Another couple went further and built the engagement ring as a cluster: a cushion tanzanite with diamonds, marquise pink sapphire and Paraiba tourmaline. The wedding bands were shaped to sit flush against it, the woman’s with milgrain detail on rose gold and the man’s kept plain to match.
Common Questions About Tanzanite
Does tanzanite only come from Tanzania?
Yes. The only commercial deposit is in the Merelani Hills near Mount Kilimanjaro. It is one of the very few gemstones with a single known source, which is part of why it is valued.
Is tanzanite hard enough for a ring?
It is 6 to 7 on the Mohs scale and has a cleavage plane, so it is softer and more fragile than sapphire or diamond. It works well in a protected setting and with a little care. For everyday wear without thinking about it, a pendant or earrings is the safer choice.
Is unheated tanzanite better than heated?
Neither is better, they are different. Heated tanzanite gives the strong blue-violet most people picture. Unheated is rarer and usually a quieter greyish-violet, chosen by people who want that softer colour and the untreated stone.
Commission a Tanzanite Piece
Every tanzanite we source is slightly different in colour and clarity, so a commission starts with choosing the stone in person, then the design. See our tanzanite engagement rings, our customised wedding bands, or the wider coloured gemstone engagement ring range, and book an appointment to see tanzanite alongside sapphire.
