John A. Jaszczak
Department of Physics and the A. E. Seaman Mineral Museum Michigan Technological University
December 5, 2014, 3:00pm Chemical Science Building, Room 101
Abstract:
The Lelatema Mountains in northern Tanzania are host to one of the world’s richest flake graphite deposits, but it is the purple-blue gem variety of zoisite called “tanzanite” that has brought renown to the region since the 1960s.
In December 2007 a pocket of exceptionally fine crystals of graphite was discovered at in Merelani’s Block D. Given graphite’s extreme softness and obvious lack of gem value, it seems almost in miraculous that specimens of these graphite crystals, perhaps the finest in the world, were superbly preserved. Adding to their uniqueness and beauty, the graphite crystals are covered by a secondary overgrowth of graphite that contains rare stellate graphite dendrites. The pocket also produced superb gem-quality crystals of diopside, fluorapatite, and tremolite crystals. More recently, world-class specimens of several sulfide minerals have been discovered and preserved. These include highly lustrous, large Pyrite crystals, exceptionally large, translucent crystals of the rare ZnS polytype wurtzite, and rare black octahedral crystals of alabandite. This illustrated lecture will briefly tour this amazing mining district, review these seemingly miraculous mineralogical that have been uncovered.