Tanzanite Sorting Goes High-Tech

Most colored gems are mined using “traditional” (read: “primitive”) techniques. A pick, a shovel, some dynamite, a few timbers, and you have yourself a mine. Recovering gems from the ensuing rubble is similarly quaint. A worker, huddled over a pile of rock or poised over a conveyor belt as rocks pass by, picks up rough crystals from the debris.

TanzaniteOne, which owns the rights to mine the prime location of the Merelani tanzanite mine in Tanzania, has changed all that. The company recently installed optical sorters, which previously had been used only for diamond mining. X-ray optical sorting machines, which replaced grease tables, recover 99 percent of all diamonds from the dirt and rock brought up from diamond mines.

Optical sorting of tanzanite is already paying dividends, according to Mervyn Dettmer, TanzaniteOne’s final-recovery manager. “Tanzanite recovery averaged out at an impressive 98 percent, with the small fraction lost being of very low grade and value,” he says.

Since the mine is expected to be played out in about 10 years, optimal recovery is crucial. To maintain its market dominance, TanzaniteOne must outpace the competition, and that requires automation. Ian Harebottle, president and chief operating officer of TanzaniteOne, is optimistic. “The installation and commissioning of this optical sorting system allows us to significantly improve the efficiency and grade of tanzanite production while reducing processing time and costs,” he said in a statement. “We aim to significantly increase throughput capacity at our Merelani tanzanite mine and enhance the profitability of our existing tanzanite operations, whilst simultaneously freeing up further capacity for future expansion.”