With its vivid blue hue, tanzanite is a geological phenomenon.

One of December’s birthstones, tanzanite is the only coloured gemstone with its own grading system. With its captivating colour, there’s no question as to the stone’s striking beauty. But, what exactly is it that makes this stone so special?

The Source

The only known source of tanzanite in the world lies at a small mining site at the foothills of Mount Kilimanjaro in Tanzania, making this sought-after gemstone a thousand times rarer than diamonds. As the story goes, a Masai tribesman came across a cluster of the intense blue crystals and alerted a local fortune hunter named Manuel D’Souza, who originally believed he had been shown a new deposit of sapphires. After further investigation, the discovery turned out to be one of the world’s latest known gems — a beautiful stone that was eventually named for its country of origin.


The best quality, most deeply saturated tanzanite gems make up just 0.13 per cent of all mined tanzanite available globally and are becoming more and more difficult to uncover. With its mystical blue colour, African heritage, and extreme rarity, the gemstone has earned a reputation for possessing magical powers — it is said to restore spiritual balance and bring good fortune to those that wear it.

The Colours

Discovered in the 1960s, tanzanite has some truly unique properties, one of which is that it is trichroic — the gemstone actually radiates three distinct colours (blue, violet and burgundy) when it is viewed from various angles and lighting conditions. The blue and violet shades are generally the most dominant colours in the stone, while the burgundy colour tends to be more noticeable in gems where violet is the most dominant shade. The colour of the finished stone depends largely on the way in which it has been cut, and vivid blue is the most sought-after hue. As with all coloured gemstones, the more vibrant and intense the colour, the more valuable the stone. Tanzanite possesses what is often considered one of the natural world’s finest shades of blue, and for this reason, the stone has become increasingly coveted.


The Structure

Tanzanite has a crystalline structure, and as such, is not easy to cut and polish. Triangular, also known as ‘trillion’ gems are the most valuable, with the round stones coming in at a close second. The resistance of the stones is assessed using the Mohs hardness scale, and with a similar hardness to the quartz family (typically 6.5-7), it is a strong gem. That said, care should be taken to avoid hard knocks and scratches, and pieces should be carefully stored when not in use.  The American Gem Trade Association declared tanzanite a December birthstone in 2002, marking the first change to their birthstone list since 1912.

The Diamond Works

The Diamond Works Institute in Cape Town demonstrates the science of polishing tanzanite, as well as the craft of transforming crystals into elegant jewellery pieces at their showroom. They also grade the gemstones at their premises and hand-select stones for their rare collection. Find out more at www.thediamondworks.co.za