This natural cluster was sourced in Afghanistan for Rocks and Things. It is rare black Elbaite cluster, not Black Tourmaline. The Elbaite crystals are encased and astride a Clear Calcite crystal (17mm). There is a strong reaction to UV light by a trace element or mineral that is not obvious in normal light.
Elbaite is an igneous mineral that almost always forms in granite pegmatites. It is a complex lithium-rich borosilicate mineral. Elbaite can be any colour of the rainbow, and crystals can be multi-coloured. Black is rare.
