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scapolite A member of the feldspathoids, of composition (Na, Ca, K)4[Al3(AlSi)3Si6O24] (Cl,SO4,CO3,OH), forming a solid solution series between the two end-members marialite (Na and Cl) and meionite (Ca and CO3); sp. gr. 2.5 (mar) to 2.7 (me); hardness 5–6; white or pale bluish or greenish; small prisms or massive; occurs in some pegmatites replacing quartz or plagioclase, but mainly in metamorphic or metasomatic rocks (see METASOMATISM). Scapolite is found in association with sphene, grossular, diopside, and epidote.