Everything you need to know about Tanzanite Gemstone

Tanzanite is a rare gem just recently discovered and can only be found in one location on Earth. This blue-violet form of zoisite was discovered for the first time in Tanzania in 1967, and Tiffany & Co. gave it the name Tanzania in honour of the country.

Tanzanite Gemstone Ring


Due to the crystals' pleochroic properties (the ability to exhibit changing hues depending on the angle of view), cutters may create gems in a wide variety of colours, from violet to bluish violet, depending on how much of the rough they choose to keep.


The mineral zoisite, a variant of which tanzanite, occurs in a range of violet to blue hues. It takes its name from the Merelani Hills in Tanzania, the only place on Earth where it is mined economically.

The property of pleochroism, which refers to the capacity of a gemstone to display changing colours depending on the direction in which the crystal is seen, has a significant impact on the look of tanzanite. Soon after its discovery, scholarly studies noted the pleochroism of tanzanite.

The pleochroic hues of the gem were characterized as "red-violet, deep blue, and golden green" in an American Mineralogist published in 1969. Heat treatment often brings out the blues and violets in a gemstone. Unfortunately, this process eliminates or greatly diminishes any yellow, green, or brown pleochroic hue.

Tanzanite Gemstone ring


Tanzanite of the highest quality may have a colour comparable to that of a good sapphire, which is a violetish blue, or it can have a colour that is mostly violet and is all it's own. Depending on the direction the cutter faces the finished gem, certain stones may take on a purple hue.

Rocking and tilting a shaped stone gently brings out its violet and blue pleochroic hues. As a result, every tanzanite includes a unique combination of these pleochroic hues.

The precise colour seen face-up is determined by several factors, including the original rough's hue, the gemstone's size, the cutter's preferred orientation for displaying pleochroic colours, and the lighting conditions. For example, blue tones in tanzanite are brought out by daylight fluorescent illumination, whereas violet to purple tones is brought out by incandescent.

Like every other kind of coloured gemstone, tanzanites are in great demand due to their attractive and eye-catching hues. In addition, pastel colours offer a softer appeal than brighter colours and are easier on the wallet.


Absorption Spectrum Birefringence Colours
Tanzanite: broad absorption in the yellow-green centred at 595 nm, weak bands at 528 and 455 nm, and a few weak lines in the red. Zoisite varieties, including tanzanite, have different birefringence values: 0.004-0.009. See "Identifying Characteristics" below. Gem-quality zoisites can be grey, green, brown, pink, or yellowish. Colour zoning may occur. Thulite can be pink. With heating, tanzanite can be blue to violet.
Birthstone Cleavage Crystallography
December Perfect Orthorhombic
Etymology Inclusions Luminescence
Zoisite is named after Baron Sigmund Zois, who presented the first specimens of the material to Abraham Gottlob Werner, the great mineralogist. Thulite is named after Thule, an ancient name for Norway. Anyolite comes from the Masai, anyone for "green." Tanzanite is the Tiffany & Co. trade name for blue zoisite, named after the country of origin, Tanzania. Zoisite may contain fingerprints, healed cracks, and growth tubes. Minerals found included in tanzanite include actinolite, graphite, and staurolite. Thulite (pink zoisite) from Nevada is sometimes medium pale brown in SW. Also, thulite from North Carolina is orange-yellow in LW.
Dispersion Enhancements Formula
0.019 (tanzanite) Virtually all tanzanite is heat treated. As a result, coatings improve colour and lustre, and some coatings add iridescence. Ca2Al3(SiO4)3(OH)
Fracture Hardness Heat Sensitivity
Conchoidal to uneven 7-Jun Yes
Occurrence Optics Phenomena
Zoisite occurs in calcareous rocks such as metamorphosed dolomites and calcareous shales subjected to regional metamorphism. Zoisites, including tanzanite, are Biaxial (+). However, thulite is Biaxial (-). Zoisite varieties have varying optic properties. See "Identifying Characteristics" below. Chatoyancy (rare, tanzanite). Surface-coated/enhanced tanzanites may show iridescence, but this is not a natural property. Colour change.
Luminescence Present Luminescence Type Lustre
Yes Fluorescent, UV-Long, UV-Short Vitreous
Optic Sign Pleochroism Special Care Instructions
Biaxial +, Biaxial - Very strong. See "Identifying Characteristics" below. Avoid rough treatment
Refractive Index Specific Gravity Transparency
Zoisite varieties, including tanzanite, have different RIs: 1.685-1.725. See "Identifying Characteristics" below. 3.09-3.38. (Tanzanite 3.35). Varies by zoisite variety, see "Identifying Characteristics" below. Tanzanite is transparent. Other gem-quality zoisites may be transparent to opaque.
Typical Treatments Variety of Wearability
Heat Treatment, Surface Coating Zoisite Good



Among precious stones, tanzanite is one of the more recent additions. In Merelani, in northern Tanzania, a Masai tribesman discovered a cluster of exceptionally translucent, bright violet-to-blue crystals weathering out of the soil in 1967. He tipped off a local fortune seeker, Manuel d'Souza, who immediately staked out four mining claims.

The new sapphire deposit D'Souza thought he'd seen gave him his hopes a boost. But, instead, one of the newest jewels in the world was hidden there.

Tanzanite Gemstone rough unpolished


In a short period of time, ninety additional claims sprung up in the same 20-square-mile region. No one knew for sure what the stunning gems were, but they were all eager to get their hands on a piece of the lucrative windfall. The new gem, which would become known as tanzanite, would ultimately become as famous as the Big 3 themselves.

Tiffany & Company signed an agreement to become the product's primary distributor and recognised its potential as a worldwide seller. So, in 1968, Tiffany launched a massive advertising effort to market the gemstone they had named after the nation of origin.

Almost immediately after its discovery, tanzanite became a favourite of renowned jewellers and gem experts and discerning consumers with a penchant for rare and exotic stones. 

It is because of its striking blue-to-violet hue, exceptional clarity, and possibility for huge cut stones this gemstone shot to rapid fame.

Stone Sizes

Only tanzanites of the several types of zoisite may grow to huge proportions suitable for cut and polished gemstones. In rough form, these stones weigh hundreds of carats.

  • 7 carats of blue tanzanite and 18.2 carats of blue cat's eye tanzanite, both from Tanzania, are on display at the Smithsonian Institution in Washington, DC.
  • Two hundred and twenty for the private collection (blue, tanzanite, Tanzania).


Tanzanite Gemstone


Stone Care

This page provides advice on how to cut and design tanzanites and other gem-quality zoisite stones.

Tanzanite Gemstone Ring care


Although tanzanite has a hardness of 6–7 on the Mohs scale, its cleavage and brittleness make it unsafe for everyday use. Use them sparingly and only in secure environments to preserve their lustre. Make sure to use a gentle brush and warm water with a light detergent.


What is so special about tanzanite?

Although it has a chemical composition with other zoisite minerals, its distinctive blue/violet hue marks it as a separate species. This trichroism only occurs in tanzanite. This implies that blue, violet and red light are emitted along each of its crystallographic axes in its unpolished state.

Is tanzanite rarer than diamonds?

According to a geologist from Tanzania, the conditions that prevailed 585 million years ago and led to the production of tanzanite were so extraordinary that the probability of discovering tanzanite anywhere else on Earth is one in a million, making it one thousand times rarer than diamonds.

Can tanzanite be worn every day?

You may wear tanzanite jewellery daily (if that's what the situation calls for), but you must do it with the greatest care. Keep in mind that this gem has excellent cleavage, which means it has a high risk of being chipped or otherwise damaged if it is subjected to a violent hit.

Can tanzanite get wet?

Tanzanites are safe to wear daily as a pendent since they are considerably more protected than in a ring. However, to this day, We still advise taking them out before engaging in physical activity, swimming, or a shower.