Sphalerite, (Zn, Fe)S, sometimes called "Black jack" or "Blende", is zinc sulphide, and is the main ore of zinc. Pure sphalerite is ZnS, but as it is usually combined with varying amounts of iron, (Fe) the formula is expressed as (Zn, Fe)S. Sphalerite with very little, or no iron can be colourless, but as in this specimen, the amount of iron has produced a dark golden brown colour. There are no complete crystals, only fractured faces, and here and there, just a glimpse of the deep red colour usually associated with sphalerite, which is a good aid for identification. The white mineral is calcite, and the specimen was collected from Snailbeach mine, Shelve, Shropshire.