Gemstone Encyclopedia / Tanzanite
Tanzanite is one of the most extraordinary gemstone discoveries of the modern era, not simply because of its color, but because of its limitation. Found exclusively in a single region at the foothills of Mount Kilimanjaro, it exists in a geological setting that has never been replicated anywhere else in the world.
Overview
This singular origin immediately separates tanzanite from nearly every other major gemstone.
Tanzanite is one of the most extraordinary gemstone discoveries of the modern era, not simply because of its color, but because of its limitation. Found exclusively in a single region at the foothills of Mount Kilimanjaro, it exists in a geological setting that has never been replicated anywhere else in the world.
This singular origin immediately separates tanzanite from nearly every other major gemstone. While diamonds, sapphires, and emeralds are mined across multiple continents, tanzanite is confined to a narrow stretch of land only a few kilometers long.
Tanzanite is a variety of zoisite, formed under a highly specific combination of heat, pressure, and chemical conditions involving vanadium. The Merelani Hills deposit in northern Tanzania represents a unique geological event: the alignment of tectonic activity, mineral presence, and environmental conditions created a zone where zoisite could develop into gem-quality tanzanite. Outside of this region, those same conditions simply do not exist.
The result is a gemstone that is not only rare in quantity, but rare in origin. It is not a stone that is scarce because it is difficult to find - it is scarce because it only exists in one place.
Discovered in 1967, when a Maasai herdsman found sparkling blue-violet crystals in the Merelani Hills and brought them to a local prospector, tanzanite was introduced to the world the following year by Tiffany & Co., which called it "the most beautiful blue stone discovered in over 2,000 years."
Colors
Tanzanite is trichroic: tilt a stone and it shifts between three distinct colors. Drag the bar or pick a color to compare.
A rich, dominant blue - the color a well-cut tanzanite shows face-up in most lighting, especially daylight.
A rich violet that shows alongside blue in a well-cut stone, giving tanzanite its complexity rather than a flat, single-note color.
A deep red-to-burgundy flash, the third and least commonly noticed of tanzanite's three pleochroic colors.
The blended blue-violet most people picture when they think of tanzanite - what a well-cut stone shows face-up once a cutter has balanced its three pleochroic colors.
A muted, brownish cast, closer to how most rough tanzanite looks before it's heated.
Colors shown are illustrations. Real stones vary with lighting, tone, and saturation. Every tanzanite color has a hardness of 6 to 7.
Properties
Mohs measures scratch resistance, from talc (1) to diamond (10).
Tanzanite ranks between 6 and 7 on the Mohs hardness scale, making it softer than sapphire and significantly softer than diamond.
This does not make it unsuitable for jewelry, but it does require a more considered approach to wear. Pieces such as earrings and pendants offer a lower-risk setting for the stone, while rings should be worn with an awareness of potential impact. Proper care and storage are essential to maintaining its condition over time.
Nearly all tanzanite on the market has been heat treated, a mild and permanent process. Select a treatment to explore it.
The 4Cs
The defining optical property of tanzanite is its trichroism, meaning it can display three distinct colors depending on viewing angle. Open each of the four Cs to see how they fit together.
The defining optical property of tanzanite is its trichroism, meaning it can display three distinct colors depending on viewing angle: blue, violet, and, in certain orientations, a flash of red or burgundy.
At its highest quality, tanzanite presents a dominant blue face-up color, supported by a rich violet undertone and, in certain orientations, subtle flashes of red or burgundy. The presence of red and violet alongside blue is not simply an interesting feature - it is part of what defines top-tier material.
Cutting plays a critical role in how these colors are presented. A well-cut tanzanite will emphasize blue while maintaining the secondary hues that give the stone its complexity. Poor orientation can result in a stone that appears flat or overly violet, diminishing its value.
See tanzanite's blue, violet, and burgundy pleochroic colors, plus its treated and untreated states, in the Colors section above.
Tanzanite is often found with relatively high clarity, especially when compared to gemstones like emerald. Eye-clean stones are common in fine material, which allows color to take center stage.
The relationship between size and color is particularly important: as tanzanite increases in size, its color typically becomes more saturated. This can enhance value, but only if the stone retains sufficient brightness - stones that become too dark lose brilliance and visual appeal.
Cut quality is essential in balancing this relationship. Proper proportions allow light to move through the stone, preserving both color and life.
A well-cut tanzanite will emphasize blue while maintaining the secondary hues that give the stone its complexity. Poor orientation can result in a stone that appears flat or overly violet, diminishing its value.
As tanzanite increases in size, its color typically becomes more saturated, which is part of why larger stones are disproportionately valuable. But that relationship only helps up to a point - a stone that grows too dark loses the brightness that makes tanzanite appealing in the first place, so size alone is never the goal.
Because tanzanite comes from a single, finite deposit, large stones with fine color are especially hard to replace once sold. That scarcity, layered on top of the deposit's own limits, is a meaningful part of what drives prices at the top of the market.
Origins & Value
Every tanzanite on Earth comes from the same roughly eight-square-mile stretch of the Merelani Hills, divided by the Tanzanian government into four numbered mining blocks with very different characters.
Origin
Block A was allocated to Kilimanjaro Mines Ltd. but has sat largely idle, a reminder of how uneven production can be even within Merelani's small footprint.
Origin
Block B is worked by small-scale local miners rather than a single large operator, alongside Block D. Together the two blocks support roughly 750 individual shafts.
Origin
Block C has been worked with mechanized, industrial methods since AFGEM took it over in 1999, and it supplies the majority of the tanzanite that reaches retail jewelry, occasionally reaching the finest AAA quality.
Origin
Block D has the strongest reputation of the four, credited with producing the rare, most intensely colored AAA-grade material collectors seek out.
In 2018, the Tanzanian government completed a 3.2-mile wall around the Merelani mining area, built to curb smuggling and formalize the supply chain with single-entry checkpoints and miner identification. It's a concrete example of the "efforts to centralize control" behind the mining disruptions described above.
Tanzanite occupies a rare position in the gemstone market where both geological limitation and market demand align.
Its single-source origin ensures that supply cannot expand, while ongoing mining challenges continue to restrict availability. As deposits become more difficult to access, the cost of extraction increases, and high-quality material becomes progressively harder to find.
The most valuable stones are those that combine strong blue-violet color, excellent clarity, and larger size. These represent the upper tier of the market and are the most sensitive to shifts in supply.
While tanzanite is often purchased for its beauty, its rarity and finite nature contribute to its long-term significance within the gemstone world.
Because heat treatment is nearly universal and standard, a report from a recognized gemological laboratory is most useful for documenting a fine tanzanite's weight, dimensions, and quality characteristics for insurance and resale.
Care
With a hardness of 6 to 7 and fair-to-poor toughness, tanzanite asks for a bit more care than harder gemstones like sapphire.
Use lukewarm water, a drop of mild soap, and a soft brush, then rinse and pat dry.
GIA specifically advises against both for tanzanite. Have it cleaned by a jeweler instead.
Extreme heat or a rapid temperature change can stress the stone.
Tanzanite is vulnerable to some acids found in cleaning products and pool or spa chemicals.
Fair-to-poor toughness and cleavage mean a sharp blow can chip or crack it. Remove rings before heavy work or sport.
Earrings and pendants are a lower-risk way to wear tanzanite than rings, which take more day-to-day impact.
Shop the stone
$4,200.00
$4,350.00
$4,350.00
$975.00
$4,250.00
$2,650.00
$3,250.00
$3,975.00
$14,500.00
$29,000.00
Shop
At Forever Rox Fine Jewelry, we focus on selecting tanzanite that demonstrates depth of color, balance, and presence.
FAQ
Tanzanite is far rarer in terms of geographic occurrence, as it is found in only one location, while diamonds are mined worldwide.
Mining closures, regulation changes, and limited supply all directly impact availability and pricing.
Deep blue with strong violet undertones and subtle red flashes is considered the highest quality.
Nearly all tanzanite is heat treated, and this is a standard and accepted practice.
It can be worn daily with care, but it is more sensitive to impact than harder gemstones.
The deposit is finite, and while supply will not disappear immediately, it is expected to decline over time.
Keep exploring
The rarest color-change gem: green in daylight, red under warm light.
A sunny, affordable quartz once called the "merchant's stone," prized for warm golden color.
The hardest natural material, prized for its brilliance and fire.
The classic green beryl, prized for vivid color and its garden of natural inclusions.
A family of gems, from deep red almandine to vivid green tsavorite.
A banded chalcedony, usually dyed a deep, uniform black, carved since antiquity.
Famous for play-of-color, flashes of spectral light that move as you do.
The only gem grown by a living creature, judged by luster, surface and shape.
A gem of many colors, including bi-color stones with pink and green in one crystal.
An opaque blue-to-green gem prized for its color and web-like matrix.
A natural gem with diamond-like fire, not to be confused with synthetic cubic zirconia.
