Transparent gypsum (variety selenite). partially terminated, has overgrown nondescript marcasite. Marcasite has a reputation for easy decomposition (especially when associated with gypsum, probably for by marcasite oxidation) but this specimen is stable: The specimen has been in my collection since 2000 and shows no signs of imminent decomposition (it lacks the typical sulfurous, metallic odor produced by decaying iron sulfides). The specimen is notable because the gypsum is unusually large for the locality.