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 colour. 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.