Calcite, CaCO3 Calcium carbonate. There is nothing very special about this specimen, except that it is one of the first specimens I collected many years ago. It is a collection of scalenahedral crystals in a limestone vugh. A few of them on the periphery are slightly larger, and all of them have a dusty coating probably derived from the presence of iron. I collected the specimen from Blaengwynlais quarry, Tongwynlais, Near Cardiff in South Wales