Tanzanite Buying Guide: 7 Expert Tips for the Perfect Gemstone
“Tanzanite is violet-blue zoisite from a single deposit in Tanzania. Learn how to judge its colour, clarity and cut, why almost all tanzanite is heated, how it is priced in India, and how to spot synthetic forsterite.”
Tanzanite is the violet-blue variety of the mineral zoisite, found in only one place on earth — a few square kilometres of the Merelani Hills in northern Tanzania — and known to the gem trade only since 1967. It is prized for its colour and for its strong pleochroism: turn it and it flashes between blue, violet and burgundy. This guide explains how to judge its colour, clarity and cut, what heating does to it, how it is priced, how to spot simulants such as synthetic forsterite, and how to care for a stone that is softer and more fragile than sapphire.
Quick answers: Tanzanite is zoisite, Mohs 6–7, with one direction of perfect cleavage, so it suits pendants and earrings better than everyday rings. Almost all tanzanite is heated to bring out its blue, and that is normal. Colour depth decides most of the price. At Ratna Gems, natural tanzanite with an independent laboratory report starts at ₹300 per carat (October 2026) — see the Tanzanite collection.
Tanzanite (Zoisite) Quick Specifications
| Chemical Formula | Calcium Aluminium Silicate with Vanadium traces [Ca₂Al₃(SiO₄)₃(OH)] |
| Mineral Species | Zoisite (Orthorhombic crystal system) |
| Optical Phenomenon | Strong Trichroism (Color shifts: Blue, Violet, Burgundy/Bronze) |
| Mohs Hardness | 6 – 7 (with one direction of perfect cleavage; needs a protective setting) |
| Specific Gravity | 3.35 (Typical density) |
| Refractive Index | 1.691 – 1.700 (birefringence about 0.008–0.013) |
| Geographic Origin | Merelani Hills, Lelatema Mountains, Manyara, Tanzania (Single Source) |
| Astrological Status | Not in classical Jyotish texts; some modern astrologers use it as a substitute for Blue Sapphire (Neelam) |
Tanzanite in Modern Astrology
Tanzanite does not appear in the classical Jyotish texts, as it was only discovered in 1967. Some modern astrologers, however, use it as a substitute (upratna) for Blue Sapphire (Neelam), linked with Saturn (Shani). The customs they follow are set out below as customs; whether any stone suits you is for your own astrologer or Pandit ji to decide.
Traditional Wearing Customs for Tanzanite
| Finger | Middle finger (Madhyama) of the working hand |
| Metal | Sterling silver, white gold or platinum; yellow gold is traditionally avoided |
| Customary Day | Saturday evening after sunset, during Shukla Paksha (the waxing moon) |
| Usual Weight | About 1 Ratti per 10 kg of body weight by custom, so about 7 Ratti for someone who weighs 70 kg. Since 1 Pukka Ratti equals 0.91 carat, 7 Ratti is about 6.37 carats. Always ask for the weight in carats on the invoice and report. |
| Custom Before Wearing | Traditionally rinsed in raw milk and Gangajal. The Shani mantra linked with it is "Om Sham Shanaishcharaya Namah" |
How to Buy an Original Tanzanite Stone: A Step-by-Step Guide
Step 1: Understand Pleochroism – Tanzanite's Colour-Changing Trait
The most distinctive characteristic of Tanzanite is its strong trichroism (a type of pleochroism). Due to its orthorhombic crystal structure and the presence of vanadium impurities, light waves split and travel along three distinct crystallographic axes, displaying three different colors when viewed from different angles:
- Deep Sapphire Blue along one axis.
- Rich Violet/Purple along the second axis.
- Red-Violet, Burgundy, or Bronze-Brown along the third axis.
How heating creates the blue: straight from the Merelani Hills, most tanzanite is brownish or bronze. Cutters heat the rough gently, typically to about 400–600°C, which removes the brown-burgundy direction and leaves the blue and violet ones. Research links the change to the vanadium in the crystal. The treatment is stable and permanent, and it is accepted throughout the trade.
Step 2: Evaluate the Color
Color is the most important value factor for Tanzanite. The most prized stones have a deep, saturated, and vivid violet-blue or pure blue color. The more intense and saturated the color, the more valuable the stone.
Step 3: Assess the Clarity & Cleanliness
High-quality Tanzanite is categorized as a Type I gemstone, which means it forms with very few natural inclusions. The finest specimens are completely "eye-clean" (showing no inclusions to the naked eye) or clean under a 10x jeweller's loupe. Avoid Tanzanites with visible internal cracks, dark mineral inclusions, or surface-reaching fissures. Because Tanzanite has perfect cleavage on the {010} plane, any internal fissure or crack acts as a structural weak point that can cause the gemstone to split or break easily under a minor mechanical impact.
Step 4: Examine the Cut and Shape (Orientation)
A well-executed cut is crucial to show tanzanite's colour and its colour shift. Because of the crystal's trichroism, the cutter must decide whether to orient the stone toward the blue direction or the violet one. Orienting for blue gives a royal-blue face-up colour but usually costs more weight from the rough; orienting for violet keeps more weight and shows more purple. Oval, cushion and trillion shapes are popular partly because they keep weight well.
Step 5: Understand What Decides the Price
The tanzanite stone price is set mainly by colour depth, then by clarity, cut and size. Deeply saturated colour in a large, clean stone is uncommon, so the price per carat rises with both depth of colour and size.
What moves a tanzanite's price
| Factor | Lower price | Higher price |
|---|---|---|
| Colour | Pale lavender or light violet-blue | Deep, saturated blue-violet |
| Clarity | Inclusions visible to the eye | Eye-clean |
| Cut | Uneven or windowed, colour leaking out | Even colour across the face, lively |
| Size | Small stones | Large stones with good colour |
At Ratna Gems, natural tanzanite with a report from an independent laboratory starts at ₹300 per carat — for example a 7.00 carat (7.69 ratti) stone for ₹2,100, with deeper-coloured stones priced higher (October 2026). Buyers who have read that tanzanite is "rarer than diamond" are often startled by this, so it is worth separating two claims. Tanzanite is geologically rare: it occurs in one small area of the Merelani Hills and nowhere else, and that deposit is finite. But rarity of source is not rarity of material. A great deal of tanzanite comes out of that deposit pale, included or small, and pale included tanzanite is not scarce. What commands the high prices is deep saturation in a large clean stone, and that is genuinely uncommon. Buyers choosing it as a Saturn stone may also want to compare Iolite (Kaka Neeli) and Lapis Lazuli, the other stones usually named as Neelam substitutes.
On "AAA" and "AAAA" grading. These labels appear constantly in tanzanite listings and they are not a standard. No laboratory issues them, no two sellers define them the same way, and a stone described as AAAA by one dealer may be ordinary commercial goods to another. Unlike diamond, coloured stone has no universally accepted colour grading scale. Judge tanzanite by what you can see — depth of blue, how much violet flashes as you turn it, whether inclusions are visible without magnification — and treat letter grades as marketing rather than measurement.
Almost all tanzanite is heated, and that is normal. Most tanzanite comes out of the ground brown, khaki or dull grey-violet, and gentle heating to about 400–600°C turns it blue-violet. Nearly everything sold as "natural tanzanite" has been heated — the stone is natural; the heating is a stable, permanent finishing step that needs no special care. Untreated blue tanzanite exists but is very rare, so a seller offering it inexpensively should be asked for a laboratory report saying so.
Step 6: Verify Authenticity and Spot Deceptive Imitations
Because natural Tanzanite is highly valuable, the market contains several imitations and simulants. Note that true "synthetic tanzanite" (lab-grown zoisite) does not exist commercially; all lab-grown claims are actually simulants. Here is how to identify them:
- Synthetic Forsterite: the best-known tanzanite imitation. It copies tanzanite's colour but has a lower refractive index (about 1.635–1.670 against tanzanite's 1.69–1.70) and a lower specific gravity (about 3.23–3.26 against 3.35). Its much higher birefringence (about 0.035 against tanzanite's 0.008–0.013) makes the back facet edges look doubled under a loupe, and it shows only two pleochroic colours where tanzanite shows three. Through a Hanneman tanzanite filter, synthetic forsterite looks green while tanzanite looks pinkish-orange.
- Cubic Zirconia (CZ) and YAG: These man-made simulants are singly refractive and will not show any pleochroism (color shift) when rotated under a dichroscope, whereas natural tanzanite always shows distinct color shifting.
- Coated stones: pale tanzanite or zoisite has been sold with a thin surface coating, including cobalt-based coatings, to imitate deep violet-blue. A coating can wear away at facet edges, and a laboratory detects it, so ask for a report that states any coating or treatment.
Critical Care, Cleavage, and Thermal Shock Warning: Tanzanite is a fragile gemstone that requires delicate handling. It has perfect cleavage on one direction, meaning a direct knock can crack the stone in two. It is also highly sensitive to thermal shock (sudden temperature changes). Never clean Tanzanite in ultrasonic cleaners (vibrations will propagate fractures along cleavage planes) or steam cleaners (heat shock will shatter it). Clean only with lukewarm soapy water and a soft-bristled brush. Never expose it to harsh household acids like hydrochloric or hydrofluoric acid.
Independent Lab Certification: Ask for a report from an independent gemological laboratory. In India, well-known names include IGI, the Gemmological Institute of India (GII) and IIGJ Research & Laboratories (formerly GTL Jaipur). A proper report confirms the stone as natural zoisite (tanzanite), records its refractive index (about 1.691–1.700) and discloses any coating or treatment. Every Ratna Gems tanzanite ships with an independent laboratory report, and you can add a GII, IIGJ or IGI report on the product page.
Step 7: Purchase from a Reputable Seller
Buy from a seller who shows the actual stone, states its weight, rate and treatment in writing, includes an independent laboratory report and will take the stone back. Our guide to buying gemstones online safely explains each check.
Why Buy Your Tanzanite from Ratna Gems?
At Ratna Gems, we describe every stone plainly and price it openly. We are your trusted source because we offer:
- Natural Tanzanite With a Lab Report: every stone comes with a report from an independent laboratory and is covered by our Authenticity Guarantee.
- Clear Pricing: natural tanzanite from ₹300 per carat, with the weight in carats and ratti on every listing.
- Help When You Need It: questions answered before and after you buy, and a 7-day return policy for eligible items.
Frequently Asked Questions
Is Tanzanite rare?
Yes. Tanzanite is mined in only one place, a strip a few kilometres long in the Merelani Hills of Tanzania, which is why it is often called a "generation stone". Like any gem, though, its future price cannot be predicted, so buy it because you love it.
Is Tanzanite a substitute (Upratna) for Blue Sapphire?
Some modern astrologers use it as one, linked with Saturn (Shani), though it is not in the classical texts. By their custom, it is set in sterling silver or white gold and worn on the middle finger, first worn on a Saturday evening.
What weight of Tanzanite is usual?
A common custom is about 1 Ratti for every 10 kg of body weight, so about 7 Ratti, or 6.37 carats, for someone who weighs 70 kg (1 Pukka Ratti = 0.91 carat).
How can I identify a fake Tanzanite or spot synthetic forsterite?
Synthetic tanzanite is not on the market, but synthetic forsterite is a well-known imitation. It has a lower refractive index (about 1.635–1.670), its high birefringence makes the back facets look doubled under a loupe, and it looks green through a Hanneman tanzanite filter where tanzanite looks pinkish-orange. A laboratory report settles it.
What is the price of tanzanite in India?
It depends mostly on colour depth, then on clarity, cut and size. At Ratna Gems, natural tanzanite with an independent laboratory report starts at ₹300 per carat, so a 7 carat stone is about ₹2,100, with deeper-coloured stones priced higher (October 2026).
Why does my Tanzanite change color under different lights?
This is due to Tanzanite's natural pleochroism (specifically trichroism). Under daylight or fluorescent light, it highlights rich royal blue hues, whereas incandescent (yellow) lighting brings out warm purple and violet-red flashes.
Can I clean my Tanzanite jewelry in an ultrasonic cleaner?
No. Tanzanite has perfect cleavage and is highly sensitive to thermal shock. Ultrasonic vibrations can cause it to crack along its cleavage lines, and hot steam cleaners can cause it to shatter. Clean only in lukewarm, soapy water using a soft brush.
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