Online Encyclopedia


Online Encyclopedia
Originally appearing in Volume V20, Page 825 of the 1911 Encyclopedia Britannica.
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PARISITE, a rare mineral, consisting of cerium, lanthanum, didymium and calcium fluo-carbonate, (CeF)2Ca(COs),. It is found only as crystals, which belong to the hexagonal system and usually have the form of acute double pyramids terminated by the basal planes; the faces of the hexagonal pyramids are striated horizontally, and parallel to the basal plane there is a perfect cleavage. The crystals are hair-brown in colour and are translucent. The hardness is 41 and the specific gravity 4.36. Light which has traversed a crystal of parisite exhibits a characteristic absorption spectrum. Until recently the only_ known occurrence of this mineral was in the famous emerald mine at Muzo in Colombia, South America, where it was found by J. J. Paris, who re-discovered and worked the mine in the early part of the 19th century; here it is associated with emerald in a bituminous limestone of Cretaceous age (see EMERALD). Closely allied to parisite, and indeed first described as such, is a mineral from the nepheline-syenite district of Julianehaab in south Greenland. To this the name synchysite (from Gr. uvryxuons, confounding) has been given. The crystals are rhombohedral (as distinct from hexagonal; they have the composition CeFCa(CO3)2, and specific gravity 2.90. At the same locality there is also found a barium-parisite, which differs from the Colombian parisite in containing barium in place of calcium, the formula being (CeF)2Ba(CO3)3: this is named cordylite on account of the club-shaped form (KOpbbXtl) a club) of its hexagonal crystals. Bastnasite is a cerium lanthanum and didymium fluo-carbonate (CeF)COa, from Bastnas, near Riddarhyttan, in Vestmanland, Sweden, and the Pike's Peak region in Colorado, U.S.A. (L. J. S.)
End of Article: PARISITE
PARK (Fr. part; Ital. parco; Sp. Marque; O.Eng. pea...

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