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clinozoisite A member of the epidote group of minerals, Ca2Al3(SiO4)3OH; sp. gr. 3.3; hardness 6.5; greyish-white to yellowish-white; crystallizes in the monoclinic system (unlike zoisite which is orthorhombic) hence the prefix ‘clino-’; massive; occurs as an alteration product of plagioclase feldspars in igneous and metamorphic rocks, particularly anorthosites, where the rock is said to be ‘saussuritized’ when feldspars are hydrothermally altered to zoisite or clinozoisite. See SAUSSURITIZATION.