What is tanzanite? A jewelry buyer explains the meaning, value, market price, and how to distinguish between fakes
In this article, we will explain the definition, history, and color characteristics of tanzanite, as well as its value evaluation criteria, market prices on the second-hand market, how to distinguish fakes and similar stones, and points to be careful when purchasing and selling. We hope this article will be able to answer any questions you may have, from those looking into tanzanite for the first time to those considering purchasing or selling it. We will also introduce the perspective of appraisal based on the practical experience of a buyer specializing in jewelry.
In a nutshell (conclusion)
Tanzanite is a blue-purple variety of the mineral zoisite, and is currently commercially mined to gem quality only in the Merelani mining area in Tanzania.It was named by Tiffany & Co. in 1968 and is known as the birthstone for December. The value is determined mostly by the intensity of the color, with general jewelry priced in the tens of thousands of yen, and high-quality, large, brand-name items priced at more than 1 million yen.
Buyer for the Komehei Group's only company specializing in jewelry. In addition to supervising the e-commerce, SNS, loose, and product production departments, he is also in charge of purchasing rare stones. He specializes in determining authenticity and evaluating value, and works to protect consumers and improve market transparency by disseminating gemological information.
Summary in 30 seconds
- Tanzanite is a blue to blue-purple gem variety of the mineral ``zoisite'', and its commercial production areas areNorthern Tanzania Merelani Block onlyIt is said that
- It is reported that it was discovered in 1967, and in 1968, Tiffany & Co. in the United States named it "Tanzanite" after the country's name.
- Strong color that changes depending on the viewing directionpleochroismIt is characterized by the fact that most of the products on the market are heat-treated to stabilize the color.
- Value is determined by ``balance of color depth and blueness,'' ``transparency,'' ``terry,'' and ``carat.'' The larger the grain, the darker the blue to violet color, the more highly valued it is.
- It has a Mohs hardness of around 6 to 7, making it susceptible to shock and rapid temperature changes, so care must be taken when handling it for daily use.
Table of contents
- What is tanzanite? Definition and basic information as a mineral
- History of tanzanite | From discovery to Tiffany's naming
- Color and pleochroism of tanzanite | Reasons for its beauty
- Four evaluation criteria to determine the value of tanzanite
- Tanzanite price/price market | Estimated purchase price
- Difference between tanzanite and sapphire
- How to identify fake and similar stones
- Points to note when purchasing
- Points to note when selling and appraising
- Care and storage
- Frequently asked questions (FAQ)
- Summary
01What is tanzanite? Definition and basic information as a mineral
Tanzanite is the distribution name for a gemstone variety of the mineral ``zoisite'' that contains vanadium and exhibits a blue to bluish-purple color.The only commercially mined area is the Merelani mining area in northern Tanzania, East Africa, and it is known as a rare gemstone that can only be found in one location in the world. It is also one of the birthstones for December.
Zoisite itself is a mineral that can be found all over the world, but it is reported that commercial quantities of gem-quality blue zoisite have only been found in Tanzania's Merelani mining area. This "concentration of production areas" is the biggest reason behind tanzanite's rarity and attention as an asset.
Basic data (mineralogical specs)
| Item | Content |
|---|---|
| Mineral name | Zoisite (Japanese name: Heilite) |
| chemical composition | Ca2Al3(Si2O7)(SiO4)O(OH) (calcium aluminum solosilicate) |
| crystal system | orthorhombic system |
| mohs hardness | 6〜7 |
| refractive index | Approximately 1.691~1.700 |
| specific gravity | Approximately 3.35 |
| color | Blue to blue-purple (colored by vanadium) |
| optical characteristics | Strong pleochroism (trichromacy) |
| Main production area | Northern Tanzania, Merelani Block (Arusha Region) |
| birthstone | december |
A gemstone that is said to be produced only in Tanzania.
In conclusion, gem-quality tanzanite is currently being mined commercially only in the Merelani mining area, located at the southern foot of Mount Kilimanjaro.Because the area that can be mined is so small, some in the industry believe that the resource could eventually run out and be exhausted within a single generation. However, it should be noted that this is a prediction of the future and is not a confirmed fact.
02History of tanzanite | From discovery to Tiffany's naming
Tanzanite was discovered in northern Tanzania in 1967, and in 1968, the American jewelry brand Tiffany & Co. marketed it under the name "Tanzanite" after the country's name, Tanzania.Although it has only been around for about 60 years, it is considered one of the most commercially successful gemstones discovered in the 20th century.
There are various theories as to how it was discovered, but one widely known theory is that blue crystals were found near Merelani, and that Mr. Manuel de Sousa, a tailor and mineral miner, registered the mining rights. It was initially thought to be a sapphire, but it has been reported that identification revealed it to be a new gemstone called blue zoisite.
03Color and pleochroism of tanzanite | Reasons for its beauty
Tanzanite's greatest appeal lies in its pleochroism, which changes color depending on the viewing direction and light source, from deep blue to violet-like violet.This color comes from trace amounts of vanadium contained in the crystal, and tends to appear bluish under daylight and purplish under incandescent light. The strength of its pleochroism also helps distinguish tanzanite from other blue gemstones such as sapphires.
What is trichromacy?
Tanzanite is a "trichromatic" gemstone that exhibits three different colors depending on the direction of the crystal (for example, blue/purple to reddish-purple/brown to yellow-green, etc.). The cutter will adjust the finished color to either ``mainly blue'' or ``mainly purple,'' depending on which direction the rough stone faces on the table (front). In general, stones that are cut so that the deep, vivid blue color shows through will have a higher market evaluation.
Heat treatment is a “standard process” for tanzanite
Most of the tanzanite on the market is said to have been heat-treated to remove the brownish color and stabilize the blue-purple color.It has been reported that freshly mined raw stones often exhibit a brown to brownish color, and that by heating them at relatively low temperatures (approximately several hundred degrees Celsius), the blue to bluish-purple color is brought out. This heating is a widely accepted standard process in the industry, and being heated does not reduce its value.
04Four evaluation criteria to determine the value of tanzanite
The value of tanzanite is comprehensively determined by four factors: (1) color (most important), (2) transparency, (3) cut, and (4) carat (weight).Of these, color has the greatest impact on evaluations; the deeper and brighter the blue to violet stones, the higher the evaluation, and the lighter the color, the lower the evaluation. It is not uncommon for the price to vary several times depending on the shade of the color, even for the same 1 carat. How to evaluate colored stones in generalArticle on evaluation criteria for colored stonesPlease also take a look.
① Color｜Dark and vivid blue received the highest rating
Deep, highly saturated blues to violet blues are more highly rated than pale lavender colors. Generally, the intensity of color is proportional to size to some extent, so dark-colored stones are more common in large stones, and small, dark-colored stones are relatively rare.
② Transparency | Must be clear to the naked eye
Facet-cut tanzanite is often available as a highly transparent stone with no inclusions visible to the naked eye. Therefore, stones with inclusions or uneven color that are visible to the naked eye will receive a negative rating, and if there are cracks that affect durability, the rating will drop significantly.
③ Terri Cut | Craftsmanship that brings out the shine
Tanzanite is highly pleochroic, so the color and shine will vary greatly depending on which direction the rough stone is facing. Stones that are cut with proportions that allow the bluish color to shine through and reflect light well are rated as having "good texture."
④ Carat｜Ratings tend to increase for 5 carats or more
Since tanzanite is produced in relatively large crystals, the price increase due to size is not as rapid as with diamonds. However, dark-colored, high-quality stones of 5 carats or more have limited circulation, so they tend to be subject to high appraisals in actual transactions.
| Evaluation items | Conditions for high evaluation | Conditions for low evaluation |
|---|---|---|
| color | Deep and vivid blue ~ violet blue | Pale lavender, strong grayish tone |
| transparency | Clean to the naked eye, no uneven color | Inclusions, cracks, and uneven color are noticeable |
| Terri Kat | Blue appears on the front and the shine is strong | Hole through the window (the center looks thin), the brightness is weak |
| carat | Dark color and large grains of 5 carats or more | Small grains and pale color |
| condition | No chips or wear | Chips on edges, scratches on surface |
Tanzanite value chart
We have compiled a list of market evaluation trends for each combination of color, size, and transparency. Actual evaluations may vary from individual to individual, but please use this as a rough guide.
| class | color | size | transparency | Market valuation trends |
|---|---|---|---|---|
| top level | Deep and vivid blue ~ violet blue | 5ct or more | Clean to the naked eye | Very expensive. Slightly distributed and subject to high appraisals |
| top | dark blue | 2~5ct | Clean to the naked eye | Expensive. Stable demand for both jewelry and loose items |
| medium | Intermediate color (blue-purple) | 1~3ct | almost clean | Standard. Center band of common jewelry |
| Popularity zone | Pale lavender to light blue | Around 1ct | There are inclusions and uneven coloring. | Limited. Evaluation of the entire product rather than a single stone |
SELBY COLLECTION
If you are looking for high quality tanzanite
At Selby, we handle tanzanite that has been purchased by jewelry buyers who have carefully determined the color, clarity, and texture of each stone. Please take a look at the lineup that we can offer because we are a specialty store that is confident in determining production areas and quality.
05Tanzanite price/price market | Estimated purchase price
The price of tanzanite varies greatly depending on quality and size, with general jewelry (rings and pendants) starting in the tens of thousands of yen, and dark-colored, large, high-quality items and branded items costing more than 1 million yen.The estimated purchase price ranges from a few thousand yen to tens of thousands of yen per carat for high-quality loose pieces, and can be valued at more than 100,000 yen for dark-colored, highly transparent pieces of 5 carats or more. On the other hand, for small, light-colored stones and side stones for jewelry, the evaluation of individual stones may be limited.
Estimated reference price (purchase/purchase)
| classification | Estimated reference price | Supplement |
|---|---|---|
| General jewelry (purchase) | Approximately tens of thousands of yen to hundreds of thousands of yen | Varies greatly depending on design, side stone, and brand |
| High quality/large jewelry (purchase) | Hundreds of thousands of yen to over 1 million yen | Dark color 5ct or more, high brand products are even higher |
| Loose purchase (around 1ct) | Several thousand yen to tens of thousands of yen | Varies greatly depending on color intensity |
| Loose purchase (5ct or more, dark color) | Cases of more than 100,000 yen | Varies depending on condition and territory |
Market trends as of 2026
In the domestic used market as of July 2026, we feel that demand for dark-colored, high-quality tanzanite remains steady. In addition to the growing interest in colored stones in general, the instability of supply due to the fact that their production is limited to Tanzania can also be cited as a factor supporting prices. On the other hand, in the distribution field, light-colored popular bands are traded at relatively stable prices, giving the impression that evaluations based on quality are increasingly polarized.
Factors that affect appraised value
| element | Impact on assessment |
|---|---|
| Color depth/blueness | The biggest impact. Stones that are mainly dark blue are highly rated. |
| carat | Dark colored stones of 5ct or more have limited distribution and are likely to be valued highly. |
| condition | Due to low hardness, chips, scratches, and cracks are a factor in reducing the price. |
| Identification book | Identification of “natural zoisite” makes transactions smoother. |
| brand | High brand products such as Tiffany & Co. may have added value. |
| Frame (bullion) | The bullion value of K18, Pt, etc. is added separately from the stone. |
06Difference between tanzanite and sapphire
Tanzanite and sapphire are both blue gemstones, but they are completely different gemstones with different mineral types, hardness, production areas, and price ranges.The biggest difference is durability: sapphire (9 on the Mohs scale) is resistant to everyday use, while tanzanite (6 to 7 on the Mohs scale) requires caution against shocks and sudden temperature changes. On the other hand, tanzanite is more affordable, and if you have the same budget, you can choose a larger stone.
| Item | tanzanite | blue sapphire |
|---|---|---|
| mineral species | Zoisite | corundum |
| mohs hardness | 6〜7 | 9 |
| color trends | Blue to blue-purple (purplish) | Blue (varies depending on production area) |
| pleochroism | Strong (color changes depending on the viewing direction) | weak to moderate |
| Main production area | Tanzania only | Sri Lanka, Myanmar, Madagascar, etc. |
| Price range trends | Tends to be more affordable than sapphire | High quality products are very expensive |
| everyday use | Handle with care (especially rings) | relatively safe |
| birthstone | december | september |
07How to identify fake and similar stones
The most widely distributed imitations of tanzanite are "synthetic forsterite" and blue glass, and for reliable identification, inspection by an identification organization is required.Synthetic forsterite is similar in color to tanzanite, but because of its high birefringence, a typical clue is that when looking inside the stone with a magnifying glass, the ridge lines of the facets appear doubled. Tanzanite's birefringence is very small, and such strong doubling is not normally observed. In addition, in recent years, there have been reports of the distribution of artificial materials colored tanzanite, such as nanoglass (glass ceramics) and YAG (artificial garnet).
Differences between natural, heated, and imitation stones
| classification | true identity | Market treatment | Main characteristics/distinguishing clues |
|---|---|---|---|
| Natural (unheated) | natural zoisite | Authentic. Distribution is in the minority | An individual that shows blue-purple color from the time of mining. Difficult to distinguish from heated products by appearance |
| Natural (heated) | Natural zoisite + heating | Authentic. Standard products account for the majority of distribution | Industry standard processing. Basically no impact on appraised value |
| synthetic forsterite | Artificial crystals of different minerals | Imitation stone (not tanzanite) | Strong doubling (ridge lines appear double) |
| Nano glass, YAG, etc. | colored artificial material | Imitation stone (not tanzanite) | There is no pleochroism, the color is too uniform, etc. Required equipment inspection |
| blue glass | glass | Imitation stone (not tanzanite) | No bubbles, swirl patterns, or pleochroism |
Self-check procedure (simple version)
- See colors by changing the light source: Check whether there is a change in expression from blue to purple under daylight and incandescent light (pleochroism). For uniform stones that do not change color at all, we will consider possibilities such as glass.
- Check doubling with a loupe: Look through the interior of the stone to the opposite facet ridge. If the lines appear clearly double, it is most likely synthetic forsterite.
- Check for bubbles and swirl patterns: If you see round bubbles or swirl patterns inside, this is a typical characteristic of glass (imitation stone).
- Check the certificate of identification: Check to see if it comes with an identification certificate from a domestic identification organization stating "Natural Zoisite".
- If you cannot make a determination, please contact a specialized organization.:The final judgment will be made by an identification organization or jewelry specialty store. Even experts cannot make a determination based on appearance alone.
08Points to note when purchasing
When purchasing tanzanite, it is important to keep in mind three points: ``check the color intensity with your own eyes,'' ``whether or not there is a certificate of authenticity,'' and ``the type of jewelry that suits the purpose.''In particular, the impression of color tends to change between photos and the real thing, and it also looks different depending on the lighting environment, so we recommend checking under multiple light sources if possible.
- Color:The price and satisfaction level vary greatly depending on whether it is light or dark colored. The basic idea is to choose a stone with the darkest possible color within your budget.
- Identification document:Choose a reliable retailer that comes with a ``natural zoisite'' identification certificate, or where you can obtain an identification certificate at a later date.
- Jewelry format:Due to its low hardness, it is not considered suitable for engagement rings that are worn every day. Pendants and earrings are resistant to shock and are recommended for first-timers.
- Nails and frame:For rings, you can rest assured with a bezel that protects the stone and a sturdy claw design.
- Value for money:Be suspicious of the risk of imitations of extremely cheap "large grain tanzanite" and check the retailer's return policy.
09Points to note when selling and appraising
Conclusion: The shortest way to get the most accurate value is to send your tanzanite to a jewelry store that has extensive experience appraising colored stones.There are two specific points for selling at a high price: ``Choose a store that specializes in colored stones,'' and ``Get the accessories you need and send them in for appraisal.'' The appraised value of tanzanite varies greatly depending on its color, so specialty stores with a track record of selling colored stones tend to be able to evaluate the value of the stone more easily than stores that mainly buy precious metals.
- Prepare the identification book, box, and warranty card.: The hassle of re-identifying stones is reduced and appraisal becomes smoother. Appraisal is possible even if lost.
- Do not force polish:Due to its low hardness, scratches caused by self-cleaning will result in a reduction in price. Just wipe it lightly with a soft cloth.
- Compare multiple stores: Colored stones are a genre that tends to have different appraisals depending on the store. We especially recommend dark-colored stones over 5 ct to be appraised at a specialty store.
- Also check the value of bullion:K18/Platinum frame will be evaluated separately for its value as bullion. Periods when bullion prices are high can be a good opportunity to sell.
SELBY appraisal/purchase
A professional buyer assesses the value of tanzanite
``The color may be light'' or ``I can't find the certificate of identification.'' If you have such items, please contact us first. As a jewelry specialty store with a track record of selling colored stones, Selby carefully assesses each stone one by one from the perspective of equipment inspection and resale. We will also thoroughly evaluate the value of the bullion separately.
10Care and storage
The basic care for tanzanite is ``warm water with diluted neutral detergent and a soft cloth,'' and the use of ultrasonic cleaners and steam cleaners should be avoided.Tanzanite has a hardness of 6 to 7, which is low among gemstones, and it has the property of being easily broken in one direction (cleavage), making it vulnerable to shock and rapid temperature changes. Please pay attention to the following points during daily handling.
- Do not use ultrasonic cleaners or steam cleaning (because there is a risk of expanding internal cracks)
- Avoid sudden changes in temperature (such as suddenly moving from outdoors in the middle of winter to indoors with heating)
- Remove when doing housework, sports, and bathing
- Store in a separate case or bag to avoid rubbing against other jewelry (especially diamonds)
- Do not hit it against hard objects (be especially careful with rings)
FAQFrequently asked questions
ENDSummary | Tanzanite is a blue-purple gemstone that can only be found in one place.
Tanzanite is a blue to blue-purple variety of zoisite that is commercially mined only in the Merelani mining area of Tanzania. In just over half a century since its naming by Tiffany & Co. in 1968, it has become a globally popular gemstone, and has even been chosen as the birthstone for December.
More than anything else, color determines value. The darker and more vivid blue to violet stones are more highly valued, and dark-colored stones of 5 carats or more are in steady demand even in the second-hand market. On the other hand, it has low hardness and is susceptible to impact, so care must be taken when handling and storing it on a daily basis.
By looking at the color and identification book when purchasing, and choosing a specialty store that specializes in colored stones when selling, you can accurately assess the value of tanzanite and enjoy it for a long time. If you are concerned about the value of the tanzanite you have lying around in your home, please consider having it appraised at a jewelry specialty store.
REFReference materials
- GIA (Gemological Institute of America) “Tanzanite” Guide (gia.edu)
- GIA Gems & Gemology Tanzanite related papers
- Mindat.org "Zoisite (var. Tanzanite)" mineral data (mindat.org)
- Handbook of Mineralogy “Zoisite” (handbookofmineralogy.org)
- Public information regarding AGTA (American Gem Trade Association) birthstones (agta.org)
- CIBJO (International Federation of Precious Metals and Jewelry) Gemstone Blue Book (cibjo.org)
- ICA (International Colored Stone Association) Tanzanite related information (gemstone.org)
- Smithsonian Institution Gem Collection Information (si.edu)
- Publication information regarding National Jewelry Wholesalers Cooperative Birthstone Revision (2021)
- Appraisal and sales practice data at Selby Co., Ltd.