Ocher is a ferruginous and siliceous alumina silicate rich in natural pigments and minerals - iron (hydr)oxides called goethite, limonite or hematite - known as dyes since prehistoric times. It is traditionally used for painting but also for protection from sun and insects, for its soothing and healing properties, for the conservation of skins before tanning, as a waterproofing or as an abrasive.