Smithsonite is zinc carbonate (ZnCO3). Also known as zinc spar, it is most often found as a secondary mineral in the weathering zone of zinc-bearing ore deposits. Its crystal system is trigonal but well-formed crystals are rare, the more common habitat being botryoidal, spherulitic or thin irregular encrustations on a rocky substrate. Colouring ranges from light green to blue, somewhat like turquoise. Actual width of specimen is 140 mm, provenance is Paterson, New Jersey, USA.