Part of Colored Gemstones A to Z
KEY NUMBERS · TANZANITE
1 source
Merelani Hills, Tanzania
Mohs 6–7
with perfect cleavage
$250–$580
per carat, 3 Bonhams results, 25 ct+
Tanzanite is the blue-to-violet variety of zoisite, mined commercially in only one place: the Merelani Hills near Arusha, Tanzania.
GIA says tanzanite is often heated at low temperatures to remove a brownish color component. It is softer than sapphire, so it needs care in rings. Color comes first in its value, and public auction results are scarce: the three we could verify, all for stones above 25 carats, ran from about $250 to $580 per carat.
TL;DR
Tanzanite is zoisite colored by vanadium. It was discovered in 1967 and named by Tiffany & Co., according to GIA.
Single commercial source: the Merelani Hills in northern Tanzania. That concentration creates scarcity and concentrates supply risk.
GIA says tanzanite is often heated at low temperatures to remove brownish tones.
GIA says deep, saturated violet blue or blue violet are the most valuable colors.
Durability is the weak point: Mohs 6 to 7. Best in earrings and pendants, or protective ring settings.
What Is Tanzanite Made Of?
Tanzanite is zoisite, a calcium aluminum silicate, colored by trace vanadium. Its defining property is strong trichroism: one crystal shows blue, violet and a brownish-yellow or burgundy color depending on direction. Cutters orient each stone to show blue-violet face-up.
Why tanzanite is heated
Much rough shows a brownish color component. GIA says heating at low temperatures removes it and produces a stronger purplish blue. Because the treatment is common, ask about it as you would for any stone.
Tanzanite, a rough crystal and a cut stone. Photo: Didier Descouens, CC BY 3.0, via Wikimedia Commons.
Where Does Tanzanite Come From?
The only commercial deposit is a strip a few kilometers long in the Merelani Hills, within sight of Kilimanjaro. Mining ranges from large concessions to small operators in deep, narrow shafts.
In 2018, Tanzania completed a wall of about 24 kilometers around the mining area to curb smuggling. In June 2020, small-scale miner Saniniu Laizer sold two rough crystals of 9.27 kg and 5.1 kg to the government for about $3.35 million, according to reports citing the mining ministry. More on the single-source story in One Hill on Earth. Nowhere Else.
Our take: "a thousand times rarer than diamond" is a sales line we cannot verify. The single commercial source is real, and it cuts both ways: it creates scarcity and concentrates political and supply risk in one small area.
This is exactly the kind of detail a sales pitch leaves out.
Every Tuesday, we publish what's actually moving in the colored stone market: auction results, producer disclosures, and the lab language that separates a good stone from a good story.
Tanzanite Price Per Carat (2026)
Tanzanite has no universal grading standard. Many sellers use "AAA," "AA" and similar letters, but those labels are commercial, not scientific, and one seller's AAA can be another's AA. Judge the stone, not the letters.
We found no reliable trade price list for tanzanite, and retail guides publish ranges that disagree widely. The public results we could verify are three large stones sold at Bonhams for about $250 to $580 per carat, including premium, in sales from 2010 and 2020. The lots and links are in our Tanzanite Price Per Carat guide.
These are older results for large stones, so they are reference points and not a price list. GIA says a tanzanite must be above five carats to have fine color, and that paler hues are more common.
What drives tanzanite value
Saturation and hue: GIA ranks deep, saturated violet blue or blue violet highest; pale lavender is more common.
Size: GIA says fine color needs a stone above about five carats.
Cut: orientation for blue face-up, and minimal windowing.
Clarity: GIA says eye-visible inclusions decrease value, particularly in lighter stones.
Is Tanzanite a Good Investment?
We do not give investment advice. The supply side is a single deposit. The resale side is harder to read: the public auction results we found are few, old and for large stones, and a handful of results does not establish a reliable return.
Tanzanite vs. Sapphire
Tanzanite | Blue sapphire | |
|---|---|---|
Mineral | Zoisite | Corundum |
Hardness | About 6 to 7, perfect cleavage | 9, no cleavage |
Color | Blue to violet, strongly trichroic | Blue, many other colors exist |
Treatment | Almost always heated | Commonly heated |
Sources | One (Tanzania) | Many worldwide |
Price | Usually cheaper than fine blue sapphire of similar size | From commercial to six figures per carat |
If the stone will be worn every day in a ring, sapphire is the safer choice. For earrings and pendants, tanzanite offers a large, saturated blue-violet for a fraction of the price. See What Is Sapphire? and Sapphire Price Per Carat.
How to Care for Tanzanite
Avoid ultrasonic and steam cleaners; use warm soapy water.
Avoid sudden temperature changes and hard knocks; cleavage makes it vulnerable.
For rings, prefer protective settings (bezel, halo) and occasional wear.
FAQ
What is tanzanite? A blue-violet variety of zoisite, colored by vanadium and found commercially only near Merelani, Tanzania.
Is tanzanite heat treated? Often. GIA says it is often heated at low temperatures to remove a brownish color component.
How much is tanzanite worth per carat? Three public Bonhams results for stones above 25 carats ran from about $250 to $580 per carat, including premium, in sales from 2010 and 2020. We found no reliable price list across all sizes and qualities.
Is tanzanite rarer than diamond? In terms of geological sources, yes: it comes from a single small area. In market terms, it is widely available today.
Is tanzanite a good investment? We do not give investment advice. A few auction results do not establish a reliable return.
Is tanzanite good for an engagement ring? It can be, with a protective setting and care, but sapphire is far more durable for daily wear.
Colored stones only make sense in context.
Supply shocks, auction results and the lab language behind the prices. Every Tuesday.
Useful Sources
GIA, Tanzanite: description, history and quality factors.
Carat Brief, Tanzanite Price Per Carat: the Bonhams results with links.
Updated November 8, 2026. Carat Brief is editorial and is not investment advice.