Delving into the mysteries of Tanzanite: an exploration of this captivating gemstone
In the foothills of Mount Kilimanjaro, nestled in the Merelani Hills of Tanzania, lies a gemstone that has captured the hearts of collectors and jewellery enthusiasts worldwide. Introduced to the market by Tiffany & Co. in 1968, tanzanite has since become synonymous with rarity, beauty, and investment potential.
This trichroic gemstone, with its distinctive purplish blue color, is a variety of zoisite, a species of gemstones with calcium aluminium silicate and hydroxyl as its composition. Tanzanite's unique color is attributed to trace elements of vanadium and chromium within its structure. It is renowned for its trichroism, an optical property that allows it to display three pleochroic colors: red-violet, deep blue, and a greenish yellow, depending on the angle from which it is viewed.
Tanzanite's allure is further heightened by its scarcity. With deposits confined to a roughly 4 km area, experts estimate that these reserves may deplete within 20 to 30 years, contributing to its rarity and potential investment value. The gem's price and value depend mainly on color, clarity, cut, and carat weight, with color being the most critical factor for desirability.
The four main commercial mines for tanzanite in Tanzania are separated into blocks A, B, C, and D. The average price of tanzanite per carat ranges from £225 to £1,100, depending on size, quality, and treatments. The largest piece of tanzanite rough reported was found in 2005 by TanzaniteOne Mining Ltd, weighing an impressive 16,839 carats (7.43lbs or 3.37kg).
The largest tanzanite ever sold at auction is the 423.56 Namunyak Tanzanite, set into an 18-carat white gold necklace with 53 carats of diamonds, which fetched over $300,000 USD at a charity sale in 2016. Comparing a number of stones can help gauge the hue and saturation of color when buying tanzanite.
When purchasing a piece of tanzanite jewelry, it is advisable to use a 10x loupe to examine the cut, clarity, and any presence of chips or cracks. The Gem-A Gemstone & Mineral Collection includes tanzanite, as well as other gemstones such as sugilite and stibnite. For those interested in starting their gemmology journey, the Gem-A offers various courses, including the Gemmology Foundation course and Short Courses and Workshops.
Approximately 270 million carats of tanzanite are mined per year, equating to 54 tonnes. The majority of tanzanite on the market today is heat-treated to enhance its color and marketability. Current projections suggest the mines will continue to produce gem quality material at the same rate for another 23 years.
In 2002, tanzanite was adopted as a new birthstone for December by the American Gem Trade Association (AGTA), further cementing its place in the world of precious gemstones. With its striking appearance, limited supply, and unique origin, tanzanite remains an attractive choice for collectors and investors, distinct from other blue gemstones like sapphire, which is harder and found in multiple locations globally.
[1] Gem-A (2021). Tanzanite. Retrieved from https://www.gem-a.com/gem-identification/gem-varieties/tanzanite/ [2] American Gem Society (2021). Tanzanite. Retrieved from https://www.americangemsociety.org/gem-encyclopedia/tanzanite [3] International Gem Society (2021). Tanzanite. Retrieved from https://www.gemsociety.org/education/gem-encyclopedia/tanzanite/
- The Merelani Hills of Tanzania house the gemstone tanzanite, a diamond alternative, synonymous with rarity, beauty, and potential investment.
- Tanzanite, a trichroic gemstone, boasts a distinctive purplish blue color and is made up of calcium aluminium silicate and hydroxyl.
- The gem's unique color is due to trace elements of vanadium and chromium within its structure.
- Tanzanite is renowned for its trichroism, displaying three pleochroic colors: red-violet, deep blue, and a greenish yellow based on viewing angle.
- The scarcity of tanzanite, with deposits only in a 4 km area, contributes to its rarity and investment value.
- The average price of tanzanite per carat ranges from £225 to £1,100, influenced by size, quality, and treatments.
- The Gem-A Gemstone & Mineral Collection features tanzanite, as well as other gemstones, and offers courses for gemmology beginners.
- In 2002, tanzanite was adopted as a December birthstone by the American Gem Trade Association, further establishing its position in the world of precious gemstones.
