Kukharenkoite-(Ce), ideally Ba2Ce(C03hF, is a new rare-earth fluorocarbonate mineral, occurring as an accessory mineral in the late REE-carbonatites and REE-rich carbonate-zeolite rocks of the Khibina massif, Kola peninsula, Russia. It has also been found in other associations within the Khibina complex as well as in the Vuorijarvi massif, Kola peninsula and the related alkaline intrusions of the Mont Saint-Hilaire complex and the Saint-Amable sill, Quebec, Canada. Kukharenkoite-(Ce) occurs in cavities as small (0.01-1.0 mm), prismatic, bladed crystals which are often in dendritic or stellate groups up to 2-3 mm across. Associated minerals are manganoan ankerite, ferroan rhodochrosite, manganoan siderite, natrolite, synchysite-(Ce), orthoclase, barite, pyrite, cordylite-(Ce), mckelveyite-(Y), ewaldite, galena and sphalerite. The mineral is yellow with a white streak; transparent with a vitreous lustre. Cleavage and parting were not observed. The microhardness VHN25 is 280(25), the Mohs hardness is 4.5; density (meas.) is 4.7(1) g/cm3 and density (calc.) is 4.62 g/cm3. The infrared absorption spectrum includes the following bands: V4685-

Karchevskyite, a new mineral related to the family of layered double hydroxides (LDHs), has been found in the Iron open pit at the Kovdor carbonatite massif, Kola Peninsula, Russia. The mineral occurs as spherulites of up to 1.5 mm in diameter composed of thin, curved lamellae. Dolomite, magnetite, quintinite-3 T , strontium carbonate, and fluorapatite are associated minerals. Karchevskyite is white in aggregates and colorless in separate platelets. Its luster is vitreous with a pearly shine on the cleavage surface. The new mineral is nonfluorescent. The Mohs hardness is 2. The cleavage is eminent (micalike), parallel to {001}. The measured density is 2.21(2) g/cm 3 , and the calculated value is 2.18(1) g/cm 3 . Karchevskyite is colorless and nonpleochroic in immersion liquids. It is uniaxial, negative, ω = 1.542(2), and ε = 1.534(2). The chemical composition (electron microprobe, average of ten point analyses, standard deviation in parentheses, wt %) is as follows:14.5(0.4) CO 2 , and 28.6 H 2 O (estimated by difference); the total is 100. The empirical formula calculated on the basis of nine Al atoms is Mg 18.00 Al 9.00 (OH) 54.00 (Sr 1.79 Mg 0.48 Ca 0.09 ) 2.36 (Ca 3 ) 8.26 (PO 4 ) 0.46 (H 2 O) 6.54 (H 3 O) 4.18 . The idealized formula is [Mg 18 Al 9 (OH) 54 ][Sr 2 (CO 3 , PO 4 ) 9 (H 2 O, H 3 O) 11 ]. The new mineral slowly dissolves in 10% HCl with weak effervescence. Karchevskyite is trigonal; possible space groups are P 3, P 3, P 1 m , P 31 m , P 312, P 312, P 3 m 1, or P 3 m 1; unit-cell dimensions are a = 16.055(6), c = 25.66(1) Å, V = 5728(7) Å 3 , Z = 3. The strongest reflections in the X-ray powder diffraction pattern [ d , ( I , %)( hkl )] are: 8.. Wavenumbers of absorption bands in the infrared spectrum of the new mineral are (cm -1 ; s is shoulder): 3470 , 3420s, 3035, 2960s, 1650, 1426, 1366, 1024, 937, 860, 779, 678, 615s, 553, 449, 386. Results of thermogravimetric analysis: total weight loss is 42.0 wt %, with three stages of loss: 12.2%, maximum rate at 230 ° C; 6.1%, maximum rate at 320 ° C; and 23.7%, maximum rate at 440 ° C. Karchevskyite is a late-stage hydrothermal mineral. The mineral is named in memory of Russian mineralogist Pavel Karchevsky (1976, who made a significant contribution to the study of carbonatites. The type material of karchevskyite is deposited at the Mineralogical Museum, Division of Mineralogy, St. Petersburg State University, and the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

No abstract