How can I tell real tanzanite from an imitation?

There is no synthetic tanzanite, so the risk is imitation rather than lab-grown material. Common simulants include synthetic forsterite, YAG sold as Tanavyte, synthetic corundum, and color-change glass. A gemologist separates them by refractive index, a Hanneman filter, and UV response. For any significant purchase, ask for a report from a recognized lab such as GIA.

Almost always. Most rough tanzanite comes out of the ground brownish and is heated to around 500 degrees Celsius to produce the blue and violet, a treatment that is stable, permanent and universally accepted in the trade. Naturally blue material exists but is rare enough that it is normally reported.

Is unheated tanzanite worth more than heated tanzanite?

No. Nearly all tanzanite is heat-treated, and unlike ruby or sapphire, that does not lower its value. Rough zoisite is usually dull brown or grey, and a moderate heat near 600°C unlocks the stable blue-violet color. GIA and AGTA treat this as a permanent, accepted enhancement, so stones are priced on color, not on treatment.

Is tanzanite running out?

The single Merelani source is finite, and mining-industry estimates commonly put commercially viable reserves at roughly twenty more years, though forecasts vary widely. The scarcity is real, but a fixed end date is a projection, not a measured fact. The durable point is simpler. There is one source, the supply is limited, and no second deposit is known.

Is tanzanite a good investment?

Treat appreciation as a possible bonus, not the reason to buy. Fine, vivid stones above three carats have risen modestly and steadily, while pale commercial goods have not. Tanzanite also trades far below sapphire of similar visual impact. If you buy, favor top color and a recognized lab report, and buy mainly because you want the stone.

What tanzanite color is most valuable?

The most prized tanzanite is a deeply saturated violetish-blue to bluish-violet in a medium-dark tone, and more blue generally sells higher than more violet. Because the gem is trichroic, it can show blue, violet, and brownish flashes from different angles, so the cutter chooses which face-up color to favor. Pale, lightly colored stones are the most affordable.

Can I wear tanzanite every day or in an engagement ring?

Tanzanite suits earrings, pendants, and occasional-wear rings better than a daily engagement ring. At 6 to 7 on the Mohs scale it is softer than sapphire, and it can cleave or chip under a sharp knock. Choose a protective setting, clean only with warm soapy water and a soft brush, and never use ultrasonic or steam cleaners.

Is tanzanite durable enough for a ring?

It is a compromise. At Mohs 6 to 7 with perfect cleavage, tanzanite is better suited to earrings and pendants than to a ring worn daily. If you do set it in a ring, choose a protective bezel or halo, and take it off for manual work and sport.

No. The blue and violet produced by heating is stable and permanent, and ordinary light and wear will not shift it. Tanzanite's real vulnerability is mechanical rather than optical, because it has one direction of cleavage and a sharp knock can split it.

Can tanzanite go in an ultrasonic cleaner?

No. Tanzanite is 6 to 7 on the Mohs scale and has one direction of perfect cleavage, which means vibration or a sharp knock can split it cleanly rather than chip it. Avoid ultrasonic and steam entirely. Clean it with lukewarm water, mild soap, and a soft cloth.

Why is tanzanite found only in Tanzania?

Tanzanite formed around 585 million years ago, when very specific pressure, heat, and vanadium-rich conditions met during the Pan-African mountain-building event. That combination is so unusual that geologists put the odds of a second deposit at under one in a million. Every natural tanzanite traces to one narrow strip in the Merelani Hills near Mount Kilimanjaro.

Where does tanzanite come from?

One place only. All tanzanite comes from a strip of the Merelani Hills near Arusha in northern Tanzania, roughly eight square kilometres in total. That single-source geology is the basis of its scarcity argument and the reason supply forecasts, rather than demand, tend to drive its long-term pricing debate.

Which month is tanzanite the birthstone for?

December, joining turquoise and zircon. Tanzanite was added in 2002, the first addition to the American birthstone list in almost a century, and it happened barely thirty years after the gem was first identified in 1967. No other birthstone was recognised so soon after discovery.

What does tanzanite symbolise?

Tanzanite has no long folklore tradition, because it was only discovered in 1967. The Maasai association with new life and the birth of children came later, and much of its modern meaning was shaped by Tiffany and Co, which named and marketed the stone rather than inheriting a name for it.

Tanzanite: A Single-Origin Discovery

History

Tanzanite is a relatively recent addition to the world of gemstones, with its discovery only dating back to 1967. A Masai tribesman named Ali Juuyawatu is credited with finding the first tanzanite crystal. It was discovered in the Merelani Hills of northern Tanzania after a wildfire exposed the gem. The initial find was mistaken for sapphires by a merchant named Manuel D'Souza. It was later confirmed to be a unique gemstone, a blue variety of zoisite, by both the British Museum and Harvard University. Tiffany & Co. then named it tanzanite, after its country of origin. This gemstone has rapidly gained popularity in fine jewellery. Tanzanite is considered a modern option for the December birthstone. It is also the gem for a 24th wedding anniversary.

Mineral Origins

Tanzanite is a variety of the mineral zoisite. It is found exclusively in the Merelani Hills at the base of Mount Kilimanjaro in Tanzania, and geologists put the odds of a second deposit forming elsewhere at under one in a million. The deposits are located within a narrow strip of land about five miles wide. Tanzanite forms in calcareous rocks such as metamorphosed dolomites and calcareous shales subjected to regional metamorphism. The gem's unique blue to violet colour is a result of trace amounts of vanadium within the zoisite. It is a relatively rare gemstone.

The 4 C's

Color

Tanzanite is known for its pleochroism, displaying different colours when viewed from different crystal directions. It is trichroic, which means it can show three colours: blue, purple, and brown. When fashioned, the gem usually displays a mix of blue and violet hues. Tanzanite's colours can range from a bright, intense blue to a violetish blue, with red flashes from within. The most prized colours are the intensely saturated violetish-blue to bluish-violet shades. In general, tanzanites with more blue are valued higher than those with more violet. Medium dark colours are considered ideal. Smaller stones often exhibit lighter colours, while larger stones above 5 carats are more likely to have the deep, saturated colours that are sought after. Tanzanite can appear blue in natural light and more violet in fluorescent light.

Clarity

Most tanzanites used in jewellery have inclusions that can only be seen under magnification. Any inclusions visible to the naked eye will decrease the value, particularly in lighter-coloured stones where the inclusions are more noticeable. Inclusions that pose durability problems, such as fractures, also lower the value. Some tanzanites may contain needle-like inclusions, which can sometimes produce a cat's eye effect.

Carat

Tanzanite is available in a variety of sizes, but the finest, deepest colours are typically seen in stones over 5 carats. Smaller stones are often less intense in colour. The price per carat increases significantly for smaller stones because of the rarity of good colour in these sizes. Large sizes of tanzanite do exist, with rough crystals weighing hundreds of carats being found.

Cut

Tanzanite is available in a variety of shapes, but cushion, trillion, and oval cuts are the most common. Cutters have to make choices about whether to cut for colour or for size, since cutting to emphasize the violet-to-purple colour usually results in less wasted rough. The cutter may choose a smaller top-colour gem over a larger, violet-purple one. Cutting orientation can also emphasize which colours are seen through the gem's crown. Deep cuts can enhance the tone of the gem. Because of tanzanite's pleochroism, an experienced lapidary is required to maximize both the size and unique colour of the stone.

Be Aware Of

Enhancements

Virtually all tanzanite is heat-treated to achieve its stable blue to violet colour. Untreated tanzanite typically appears dull grey or brown. GIA and AGTA treat this heat as a permanent, accepted enhancement that does not affect the price. There is no widely accepted method for confirming heat treatment. Some tanzanites may have surface coatings applied to improve colour and luster, or to add iridescence. These coatings tend to wear off the facet edges first.

Simulants

While no synthetic tanzanite exists, there are several simulants available. These include: synthetic forsterite, which can be identified by its doubled back facets and lower refractive index, synthetic yttrium aluminum garnet (YAG), also known as Tanavyte, which is harder than tanzanite and has a higher refractive index, synthetic corundum, such as Coranite, which appears grey-green under a Hanneman filter, and various kinds of glass, including colour-change glass. Most imitations can be identified with a Hanneman filter or by UV fluorescence.

Synthetics

Currently, there are no known synthetic tanzanites.

Final Thoughts

Buying Tips

When buying tanzanite, consider that a medium dark, slightly violet blue is the most desired colour. The stone should have good transparency and an intense colour. Be aware that the colour is less saturated in smaller sizes, and that stones above 5 carats are more likely to have a fine colour. Choose a stone with a good cut, which allows light to reflect evenly across the entire gem. Given tanzanite's pleochroism, the cut will determine the face-up colour, so consider whether a more blue or more violet hue is preferred. It is always safe to assume that a blue to violet tanzanite has been heat-treated. It is also important to work with a knowledgeable jeweler who can show you quality differences.

Jewelry Care

Tanzanite has a hardness of 6 to 7, making it softer than many other gemstones. It also has a tendency to cleave and can be brittle. This means tanzanite is not the best choice for daily wear, especially in rings, and it requires a protective setting. For occasional wear, tanzanite is suitable for earrings, necklaces, and tie clips. When cleaning tanzanite jewelry, use only warm soapy water and a soft brush. Never put tanzanite in an ultrasonic machine or subject it to steam. Store tanzanite pieces in their own protective pouch to avoid scratching or chipping.

Sources

Cited gemological sources
Authority	Title	URL
GIA	Gemological Institute of America, Tanzanite encyclopedia + quality factors	gia.edu/tanzanite
IGS	International Gem Society, Tanzanite buying guide + Tanzanite (Zoisite) value, price, and jewelry information	gemsociety.org/article/tanzanite-jewelry-and-gemstone-information
AGTA	American Gem Trade Association, Tanzanite (December birthstone) reference	agta.org/gemstones/tanzanite