Real Treasures Within The Earth...Pt 3

Natural trichroic tanzanite seen under incandescent lighting conditions.

You can only imagine what it must be like waking up 6 am every morning 5 days a week, sometimes 6 days a week, on a colored gemstone mine. Its not like a commercial commodity mine where the goal is to move thousands, sometimes tens of thousands of tonnes of rock a day. There is also very little, if any, security required to secure the ore as it is tied up in the rock, and any single piece will only have a couple parts per million of gold, silver, copper, etc. The Block C tanzanite mine was the complete opposite. The presence of security and regular searching was a requirement, and formed a signifiant department of operations on the mine. Every miner, geologist and surveyor had a 'security' role as it increasing the number of eyes to spot gems and to stop the theft. 

Askari Shaft is/was one of the central shafts on Block C sunk near the property's small dirt landing strip. The name comes from a small police watch point which was originally located nearby (prior to the landing strip). And so you might have worked out that 'Askari' means 'policeman' in Swahili. In the early days, it was a steep shaft winding its way into the depths of the tanzanite deposit, first through 30m of a calcrete (cemented) alluvial layer covering most of Block C, D and D Extension of the Merelani Hills, and then into the 2 billion year old metamorphic schists and gneisses, and the tanzanite host rock and ore. 

Shafts were sunk to intercept and cut across the ore body. Then drives were created along the ore in both directions. The Askari Shaft always gave us above average, good crystals with very good clarity and color. On 28 April 2005, in Level 10 (essentially 100m down the shaft), the (above) photograph was taken. This day was no exception with the chunks of tanzanite easily sharing its strong and inherent tri-chroism to be captured in the most original, most famous and most beautiful way. The natural orthorhombic crystal shape of tanzanite can also be seen. The real treasures from within the earth show the crystal's termination with the (top left) blue a-axis; the long, prismatic shape can be seen on the (bottom) violet b-axis, and the square (can also be rectangle) shape can be seen on the (top right) brown c-axis.