• journal_title：The Canadian Mineralogist
• Contributor：Joel D. Grice ; Robert A. Gault ; Ralph Rowe ; Ole Johnsen
• Publisher：Mineralogical Association of Canada
• Date：2006-
• Format：text/html
• Language：en
• Identifier：10.2113/gscanmin.44.5.1137
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：44
• issue：5
• firstpage：1137
• section：Articles

id="p-1">Qaqarssukite-(Ce), ideally BaCe(CO₃)₂F, is a newly identified mineral species from the Qaqarssuk carbonatite complex, southern West Greenland. It occurs as yellow-brown to brown individual crystals or aggregates. These crystals are up to 50 μm, and aggregates attain 2 mm across. The mineral comprises a significant amount of the potential ore at this locality. Associated minerals include calcite, dolomite, strontianite, phlogopite and pyrite. The mineral has a subadamantine to greasy luster and a white streak. It is soft (Mohs hardness 3–4) and brittle, with an uneven fracture. Qaqarssukite-(Ce) is uniaxial positive, ω 1.672(3), ε 1.751(5), and is nonpleochroic. It is trigonal, space group P3̅c1, with unit-cell parameters refined from powder-diffraction data: a 7.2036(9), c 18.172(3) Å, V 816.6(2) ų and Z = 6. The strongest eight X-ray powder-diffraction lines [d in Å(I)(hkl)] are: 5.14(28)(102), 4.55(43)(004), 3.671(32)(104), 3.534(41)(111), 3.348(100)(112), 3.093(40)(113), 2.569(35)(204) and 2.078(60)(300). Electron-microprobe and crystal-structure analyses yield CaO 2.82, SrO 3.92, BaO 27.41, La₂O₃ 8.82, Ce₂O₃ 20.26, Pr₂O₃ 1.85, Nd₂O₃ 6.64, Sm₂O₃ 0.37, Eu₂O₃ 0.18, TiO₂ 1.41, P₂O₅ 0.05, F 5.04, CO₂ (23.00), O = F −2.12, total 99.65 wt.%. The empirical formula, based on seven anions and two [CO₃] groups, is (Ba_0.68Ca_0.19Sr_0.14)_∑1.01 (Ce_0.47La_0.21Nd_0.15Pr_0.04Sm_0.01Ti_0.07)_∑0.95 (CO₃)₂ F_1.01. The density calculated from the empirical formula is 4.64 g/cm3. The structure has been refined to R = 0.111. The structure has three chemically distinct layers parallel to (001): (1) carbonate groups oriented perpendicular to the layering, (2) a layer of Ce–O–F polyhedra, and (3) a layer of Ba–O–F polyhedra. Qaqarssukite-(Ce) has a polymorphic relationship with huanghoite-(Ce), but the crystal structure resembles that of synchysite-(Ce). The mineral is named after the locality.