Recently the Carlsbad laboratory received a 1.33 ct transparent brownish orange pear brilliant for identification service (see above). Standard gemological testing revealed a refractive index from 1.670–1.750 with a birefringence of 0.080 and a specific gravity (obtained hydrostatically) of 4.40. There was no fluorescence observed with exposure to long- or short-wave UV light. The stone also appeared doubly refractive when examined with polarized light. Microscopic examination with a fiber-optic light source showed strong doubling, two-phase fingerprints with trapped liquid and gas, and crystal inclusions. Raman and mid-IR spectroscopy conclusively identified the stone as parisite-Ce. The Raman spectrum displayed the strongest vibrational band at 1083 cm–1, and subsequent peaks at 1740, 1567, 1431, 741, 398, and 269 cm–1, which positively identified the mineral. The mid-IR spectrum revealed areas of rare earth element (REE) absorption. Energy-dispersive X-ray fluorescence (EDXRF) analysis detected Ce, La, and Ca, supporting this identification.
Parasite is one of the rare-earth carbonite minerals found in the bastnäsite group, with a chemical formula of Ca(Ce,La,Nd)2(CO3)3F2. Parisite crystals are found in carbonatites, granite pegmatites, alkaline syenites, and hydrothermal deposits associated with these environments. Normally the crystals of parisite are too small and cloudy to produce decent gemstones. They are usually found as mineral inclusions in emerald from the Muzo mine in Colombia and in quartz from Zagi Mountain, Pakistan. This is the first time a faceted parisite gem has been examined by GIA.
Recently the Carlsbad laboratory received a 1.33 ct transparent brownish orange pear brilliant for identification service (see above). Standard gemological testing revealed a refractive index from 1.670–1.750 with a birefringence of 0.080 and a specific gravity (obtained hydrostatically) of 4.40. There was no fluorescence observed with exposure to long- or short-wave UV light. The stone also appeared doubly refractive when examined with polarized light. Microscopic examination with a fiber-optic light source showed strong doubling, two-phase fingerprints with trapped liquid and gas, and crystal inclusions. Raman and mid-IR spectroscopy conclusively identified the stone as parisite-Ce. The Raman spectrum displayed the strongest vibrational band at 1083 cm–1, and subsequent peaks at 1740, 1567, 1431, 741, 398, and 269 cm–1, which positively identified the mineral. The mid-IR spectrum revealed areas of rare earth element (REE) absorption. Energy-dispersive X-ray fluorescence (EDXRF) analysis detected Ce, La, and Ca, supporting this identification.
Parasite is one of the rare-earth carbonite minerals found in the bastnäsite group, with a chemical formula of Ca(Ce,La,Nd)2(CO3)3F2. Parisite crystals are found in carbonatites, granite pegmatites, alkaline syenites, and hydrothermal deposits associated with these environments. Normally the crystals of parisite are too small and cloudy to produce decent gemstones. They are usually found as mineral inclusions in emerald from the Muzo mine in Colombia and in quartz from Zagi Mountain, Pakistan. This is the first time a faceted parisite gem has been examined by GIA.
