The core of the specimen is massive to crystalline sphalerite, having an orange-brown to dark brown color and slightly iridescent surface. Across this surface are peppered numerous small and brassy chalcopyrite crystals. Of greatest interest here is the 7 mm gypsum blade perched on one sphalerite face. Gypsum is uncommon in Joplin Field mines (Mindat doesn't list this mineral for the locality), although its presence is quite reasonable, formed by oxidation of the abundant sulfide minerals in this deposit.