BARYTES, HEAVY SPAR

(BaSO,), orthorhombic mineral occurring in metalliferous veins; known as cawk in Derby shire lead-mines; sp. gr. 4.5; used as ‘permanent white’ pigment. clinic white transparent crystals, found only at Alston Moor, Cumber land, England. with dark cleavage surfaces, weathering to turbid shades; composition varied, chiefly felspars, olivine, augite, black hornblende, biotite, and nepheline, together with grains of magnetite; many are characterized by columnar jointing, producing picturesque conformations, of which Staff a and Giant’s Causeway are well-known examples. light peaked helmet, worn with or without a movable front, in common use during reigns of Edward I., II., IN., and Richard ITI.