Zinc ore occurs in two types of deposit: as primary zinc ore in thin veins known as rakes, or a secondary deposit formed by weathering of the primary mineral veins. Zinc ore is most commonly found as zinc carbonate (ZnCO3), known as calamine or smithsonite. It generally occurs as rounded, crystalline crusts or granular, honeycombed masses that have a vitreous or pearly luster and are typically dirty brown or grey in color. Locally it was known as ‘dry bone’ ore, having a cellular to spongy appearance reminiscent of dry bone. Calamine is actually a secondary mineral, found principally in the oxidized zone of the zinc-bearing ore deposits. It is derived from the alteration of the primary zinc sulphide (ZnS) mineral sphalerite. This is generally a dark grey or black, highly lustrous mineral, but can vary in appearance. Both occur on Mendip.
Its chief use was to make brass by mixing with copper