Lantanita de Curitiba, Paraná

Resumo

Minute am ethystine crystals of lanthanite w ere found covering fissure, surfaces of carbonate concretions in sedimentary pleistocene rocks at Curitiba, State of Paraná. The crystals show platy (001) habit, bounded by very narrow (100) (010) (110) and (111) faces. B esides m icaceous (001) cleavage,, tw o other parting (? ) directions w ere also observed. The crystals are invariably twinned according to (110) plane. Four pairs cross groups are common. Optical data are given . Some amount of rare earths of the cerium group m ay have been concentrated into ashes through prolonged plant decay. The lanthanite crystals would be the result of extration of lanthanum from ionic soil solutions, fixation on the surfaces of som e colloidal body (p silom elane in case) and final crystallization