Sphalerite on Calcite

Perhaps the most rarely seen sulfide, in geodized brachiopods from Georgetown, is Sphalerite. Although approximately one third of geodized brachiopods will have Pyrite, Marcasite or Goethite, less than 1 in 100 will house Sphalerite. Sphalerite, at this locality, tends to form small dark reddish brown to black crystal groups and masses. This mineral will form…