Jeffersonite is the very rare zincian manganoan variety of augite, a clinopyroxene and was originally described from Franklin. This aesthetic cluster of lightweight, brownish crystals is dominated by the large, sharply terminated crystal, which is, in fact, doubly terminated. Old-time, classic and seldom-seen material. Comes with an expertly handwritten, faded label from an older collection. The collection this came out of was a museum stash dating to prior to World War I.