Barytes, Barium Sulphate, is an ore of the metal Barium (Ba). It is usually found in veins of Lead (Pb) and Zinc (Zn) ores. It is used in the chemical, paint and paper industries, as well as rubber. In paper-making Barytes is added to improve the paper's finish - levelling it and giving it a gloss, as a slip and filler respectively. It was not mined commercially in the North Pennines orefield till the later 19th century. It can also be found when Barium Chloride brines mix with sulphate waters. This was first noted as a concretion to mine equipment, where it could cause blockages.