• journal_title：The Canadian Mineralogist
• Contributor：Henrik Friis ; Tonći Balić-Žunić ; Igor V. Pekov ; Ole V. Petersen
• Publisher：Mineralogical Association of Canada
• Date：2004-
• Format：text/html
• Language：en
• Identifier：10.2113/gscanmin.42.1.95
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：42
• issue：1
• firstpage：95
• section：Articles

Kuannersuite-(Ce) is a new mineral species belonging to the apatite group. It was found in the Ilímaussaq alkaline complex, South Greenland, and occurs as light rose-colored hexagonal prismatic crystals, up to 1.5 mm long, with a white streak and a vitreous luster. Associated minerals include aegirine, analcime, beryllite, chkalovite, galena, gmelinite, gonnardite, lovdarite, nabesite, neptunite, pectolite, polylithionite, pyrochlore, sphalerite and tugtupite. It is brittle with an uneven fracture, and poor {001} and {100} cleavages, and a Mohs hardness of 4½ – 5½. Although kuannersuite-(Ce) is trigonal and uniaxial negative with ε= 1.669(1) and ω = 1.694(1), it has a 2V(meas.) of 10 to 20°. The empirical formula based on results of electron-microprobe analyses and calculated with 26 anions is: (Ba_5.61Sr_0.15K_0.03)_∑5.79Na_2.14(Ce_1.00Nd_0.43La_0.25Sm_0.05Th_0.02Pr_0.01)_∑1.76 (P_6.02Si_0.14)_∑6.16O_23.72(F_1.70Cl_0.58)_∑2.28 or, ideally, Ba₆Na₂REE₂(PO₄)₆FCl. The strongest X-ray-diffraction lines [d in Å (I)(hkl)] are: 2.969(100)(211,112), 2.867(60)(300), 1.965(80)(320,213). The crystal structure was refined (R = 2.79%) in space group P3̅, with a 9.9097(6) Å, c 7.4026(6) Å, V 629.42(7) ų, Z = 1 and D_calc. = 4.51(1) g/cm³. Ba, REE and Na are distributed over different structural sites with distinct atomic coordinations, whereas F and Cl occupy positions in two different octahedrally coordinated voids formed by Ba atoms, with distances typical for a regular six-fold coordination of these anions. Cl is incorporated only in the larger of the two coordination polyhedra. A comparative analysis of the crystal chemistry of kuannersuite-(Ce) and related Ba and Sr phases from the apatite family is reported.