Tanzanite is the blue variety of the mineral Zoisite and the birthstone of December. It is a relatively newly discovered gemstone, only unearthed in 1967 in Northern Tanzania. It was first made popular by Tiffany & Co, who gave it the trade name of Tanzanite. It is named after its origin Tanzania, which is still the only deposit of economic importance. Although only widely recognised by people after 1967, Tanzanite has been known to be the second most popular blue gemstone, right after Sapphire.
History & Lore
The biggest Tanzanite rough ever unearthed is the Mawenzi. Named after Mount Kilamanjaro’s second highest peak, the rough weighs at 16,839 cts. Famous London based designer Kat Florence designed and sold a 423.56 cts flawless Royal Velvet blue Namunyak Tanzanite at a charity auction for victims of Nepal earthquake, part of the proceeds is used to build a school in Nepal. That gemstone is the biggest Tanzanite ever offered at an auction, which auctioned off for a total of around USD 300,000.
In our inventory, we have a 39.75 cts Bluish Violet eyeclean Tanzanite pendant adorned with 7 large diamonds with a approx total weigh of 10 cts. It is one of our masterpieces and available for sale.
Tanzanite colours range from violetish-blue to bluish-violet to violetish-purple, there is no widely accepted Tanzanite colour grading systems as of now. The highest valued Tanzanites are more on the violetish-blue scale looking close to top quality sapphires. However, some may feel that the Tanzanite colours with a distinctive violet hue is more desirable. The finest colours are usually seen in stones above 5 cts as smaller stones generally exhibit lower saturation.
Viewing at different angles, Tanzanite’s hue may appear violet. In some exceptional Tanzanites, the colour is predominately an intense violetish-blue with red flashes of pleochroic color coming from within the stone. Bi-coloured Tanzanites are also traded in the industry, however they are less expensive as the colours are most often too dark or not saturated.
Most Tanzanites sold on the market are of eye clean quality, this means that inclusions will only be seen under magnification. Any Tanzanites with eye visible inclusions will definitely be offered at a lower price than normal Tanzanites that are eye clean, given the availability of the latter. We do recommend to only get eye clean Tanzanites. In rare cases, parallel needle-like inclusions may give a stone a cat’s-eye effect.
Tanzanites only comes from Tanzania, as the name implied. The mining operations in Tanzania is divided into 4 blocks: A,B,C,D - with A & C offered to large companies, B & D offered to local miners. There has been a saying that block D produces the best quality Tanzanites. The only known source in the world is the Merelani Hills near Mount Kilimanjaro in Northern Tanzania.
Tanzanites of desirable colours are known to be treated by heat. The prevalence of such treatments makes gemstone testing laboratories such as GIA assume that Tanzanites are heated by default. Unheated Tanzanites are generally brown in colour, with the deeper browns changing into more saturated blue Tanzanites after heat treatment. However in very rare occurrences, blue saturated Tanzanites can be found naturally, although they are probably naturally heated by wildfires that create the same treatment effect on them underground. These stones are highly sought after and valued by collectors. An interesting fact is that these Tanzanites are often found in block D, which might be why the rumours of block D having the best Tanzanites mined.
Rarely, fracture filling and colour coating on the pavilion of a stone gives a desirable but temporary result. We do not recommend buying Tanzanites with such treatments.
Synthetic Tanzanites do exist in the trade and is offered by many companies. We recommend only buying Tanzanites only from reputable dealers or those with laboratory certificates. Tanzanites often does not come with certificates, so this is crucial in ensuring that your Tanzanite is natural.
With a Mohs scale rating of 6-7, Tanzanites can be durable gemstones for jewellery but has to be carefully stored and taken care of, as its more likely to be scratched. Tanzanite is to be cleaned with warm soapy water and a soft brush.