Parisite: Gemstone Information
Parisite may be parisite-(Ce) or parisite-(Nd). It is convenient to write the composition as Ca(Ce,Nd,La)2(CO3)3F2. Monoclinic, pseudohexagonal crystals are transparent to translucent brownish yellow, orange to brown with hardness 4.5 and SG 4.36. The RI for the ordinary and extraordinary rays is 1.671–1.676 and 1.771–1.757, uniaxial positive with birefringence 0.081. Parisite occurs in carbonaceous shales including those hosting emeralds in the Muzo district, Boyaca, Colombia, and as inclusions in the emeralds. The occasional star stone has been reported. An RE absorption spectrum could be expected when the Nd content is significant.