This quartz variety is a real oddity. It consist of smoky quartz crystals, usually very clear, with dispersed halos of darker spots on the surface. The color is just on the surface and doesn’t penetrate too deep in the quartz so the gemstones have to be cut using the quartz face as the base and watching the spots through the quartz.
The genesis of Dalmatine quartz is very interesting, they are irradiation halos, caused by a natural irradiation from small radioactive crystals formed on the face of the quartz crystal. The radioactive crystals was probably of Uraninite or just Zircon and they have been completely destroyed, probably by the atomic decay. So now the stone are absolutely radiation free and there is no ealth risk.
This deposit was furstly found in 2006 in the Gameleira pegmatite near Medina in northern Minas Gerais.