Q. What is the birthstone for December? A. Tanzanite

There is a reason, why the name tanzanite sounds so similar to the east African country Tanzania. It’s because this blue/violet gemstone originates in Tanzania and can only be mined in a very small area in Mirerani Hills in Manyara region. What exactly is tanzanite, the second most popular blue gemstone after sapphire? 

What is tanzanite? Tanzanite is a variety of mineral zoisite. Chemically tanzanite consists of calcium aluminum silicate hydroxide. It is highly trichroic and appears in varying colours, when viewed from three different angles. In its rough state, tanzanite usually appears with a reddish brown hue and only after heat treatment the deep violet blue colour is unveiled, which then makes it dichroic and only two colours remain. Heat treatment does not affect the price of the finished gemstone as this process is universal. Most tanzanite stones are under five carat weight and ones above it are very rare.

Tanzanite origins Tanzanite is considered a late addition to the gemstone family as it was only discovered in the 1960s in commercial quantities. At first it was mistaken for different minerals and only after several examinations it was announced to be a variety of blue zoisite. 

After Tiffany & Co. realised that the beautiful new gem would be hard to retail due to its unappealing name blue zoisite, they renamed the gemstone tanzanite to spark customer interest and imply its rarity. The name clearly suggested that the location, where the gem could be found, was Tanzania. Since then, tanzanite has become significantly popular and is the second most sought-after blue gemstone after sapphire. To this day, Tiffany & Co. has one of the largest tanzanite collection in the world. 

In 2005 the largest tanzanite stone was found 885 feet below ground - measured at 8.6 by 3 by 2.7 inches, this 16 389-karat stone weighed 7.2 pounds. An outstanding find due to its vivid blue colour and size. It was named Mawenzi, the second highest peak on Mount Kilimanjaro. The reason, why it was named after the second highest peak, was that an even bigger stone was expected to be found someday, which then would claim the name of the highest peak, Uhuru. 

Tanzanite and other blue gemstones If looking at the blue gemstone market, tanzanite is among top four commercially popular blue gems, the other three being sapphire, aquamarine, and topaz. Tanzanite excels with its rarity. Not only is it more rare than the aforementioned blue gemstones, but it is even more rare than diamonds. 

Tanzanite is almost as favoured as sapphire. To an untrained eye both stones may seem practically the same. The main difference between them is that sapphire scores slightly higher on the mineral hardness scale, however both stones are luxurious, highly valuable, and an excellent investment. Skillful jewelleryknow the best uses of tanzanite and can consult the customer on suggested uses to make this beautiful stone outshine many other gemstones.

Tanzanite use in jewellery As a gemstone tanzanite is suitable for jewellery that is less likely to encounter abrasion, like earrings and pendants. When used in rings, it should be used on special occasions rather than daily wear. A knowledgeable jeweller will always be able to make the best suggestion for the customer to meet their expectations and to truly showcase the exceptional beauty of this blue gemstone.


Almost all tanzanite on the market has gone through heat treatment to remove the reddish brown hue so that only blue violet colour remains. However, some paler stones have been known to be coated with cobalt, which should be avoided and clearly disclosed to customers purchasing tanzanite jewellery as the coating wears off with time. Heat-treated stones do not undergo natural colour changes and should retain their original colour. This, again, is something that experienced jewellers will make known to their customers.

Tanzanite value Tanzanite stones showing deeper colour blue rather than lighter blue or violet are valued higher on the market. Naturally, the size and clarity of the gem are major factors, when determining the price. Other factors include type of cut, tanzanite demand, as well as the current supply of the mineral in Tanzania. 

If you are looking for a deep-blue jewellery item to add to your collection, tanzanite is one to consider. It is luxurious, and more affordable than sapphire, and due to its high demand and single mining source, it is predicted to become even more valuable in the future.  


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