Calcite, CaCO3 calcium carbonate. There is nothing remarkable about this specimen. It is simply a lump of massive calcite, included in this collection only because I took a fancy to it when I visited the Snailbeach mine in Shropshire, about 15 years ago. There is an enormous amount of this gangue mineral at the mine, which was the largest lead mine in Shropshire. The calcite on the waste tips is very often found in association with sphalerite. or with sphalerite inclusions. Tested with a U.V. light it fluoresces a pale red.