Carbobystrite, Na8[AI6Si6O 24](CO3)·4H2O, a new Cancrinite-group mineral species from the Khibina alkaline massif, Kola peninsula, Russia : description and crystal structure

Carbobystrite, ideally Na8[Al6Si6O 24](CO3)\ub74H2O, trigonal, a 12.6678(5), c 10.3401(4) \uc5, V 1437.0(2) \uc53, c:a = 0.8162, space group P31c, Z = 2,R = 0.0271 (for 4861 observed reflections collected with a four-circle X-ray diffractometer), is a new cancrinite-group mineral species from Mount Koashva, Khibina alkaline massif, Kola Peninsula, Russia. It formed in a pegmatitic environment. Associated minerals are: microcline, sodalite, megakalsilite, natrolite, pectolite, aegirine, natrite, nacaphite, vitusite-(Ce), fluorcaphite, belovite-(Ce), umbite, lemmleinite-K, lomonosovite, lovozerite, phlogopite, sphalerite and galena. The mineral was found in only one hand specimen of pegmatite as a corroded irregularly shaped grain about 3 mm across, intergrown with sodalite, megakalsilite and natrite. It is transparent, colorless with a white streak, a vitreous luster, and fluoresces pale yellow under ultraviolet light. rbobystrite has a Mohs hardness of 6, is brittle with a conchoidal fracture, and has no cleavage. The calculated density is 2.366 g/cm3. Carbobystrite is uniaxial negative, non-pleochroic, \u3c9 1.500(2), \u3b5 1.488 (2). The strongest six reflections in the X-ray powder-diffraction pattern [d in \uc5(I)(hkl)] are: 4.689(100)(012), 3.249(100)(1\u30432, 122), 6.378(80) (1\u30420), 2.661(80)(041, 123, 1\u30433), 3.867(70)(1\u30431, 121), and 3.664(70)(030). An electron-microprobe analysis gives Na2O 22.66, K2O 1.75, SiO2 35.74, A12O3 30.42, CO24.37, H2O 6.26, sum 101.20 wt.%, with CO2 and H2O calculated from structural data. The empirical formula (based on O = 30.5 atoms per formula unit) is (Na7.40K0.38)\u3a3 7.78(Al6.04Si6.02) \u3a312.06(CO3)\ub73.5H2O; the simplified formula is Nag[Al6 i6O24](CO 3)\ub74H2O. The name carbobystrite denotes the compositional relation between the new mineral and bystrite, (Na,K) 7Ca[Al6Si6O24](S) 1.5\ub7H2O they are related by the substitution Na+ + (CO3)2-+ 2.5H2O -\u2192 Ca2+ + (S2-)1.5. The framework of Si,Al-O tetrahedra can be described as an ABAC stacking sequence. In the crystal structure, there are two LOSOD cages, and two e (cancrinite) cages per unit cell, giving a maximum of two (CO3) groups and six H2O groups for the LOSOD-type cages and two H2O groups for the cancrinite cages, respectively. This is the first complex-sequence cancrinite-group mineral with (CO3) groups in cages larger than the cancrinite cages. Carbobystrite suggests a new series of carbonate equivalents of all known complex sequences in the cancrinite group

Kolskyite, (Ca□)Na2Ti4(Si2O7)2O4(H2O)7, a group-IV Ti-disilicate mineral from the Khibiny alkaline massif, Kola Peninsula, Russia : description and crystal structure

Kolskyite, (Ca\u25a1)Na2Ti4(Si2O7)2O4(H2O)7, is a Group-IV TS-block mineral from the Kirovskii mine, Mount Kukisvumchorr, Khibiny alkaline massif, Kola Peninsula, Russia. The mineral occurs as single, platy crystals 2-40 \u3bcm thick and up to 500 \u3bcm across. It is pinkish yellow, with a white streak and a vitreous luster. The mineral formed in a pegmatite as a result of hydrothermal activity. Associated minerals are natrolite, nechelyustovite, kazanskyite, barytolamprophyllite, hydroxylapatite, belovite-(La), belovite-(Ce), gaidonnayite, nenadkevichite, epididymite, apophyllite-(KF), and sphalerite. Kolskyite has perfect cleavage on 001, splintery fracture, and a Mohs hardness of 3. Its calculated density is 2.509 g/cm3. Kolskyite is biaxial negative with \u3b1 1.669, \u3b2 1.701, \u3b3 1.720 (\u3bb 590 nm), 2Vmeas. = 73.6(5)\ub0 , 2Vcalc. = 74.0\ub0 , with no discernible dispersion. It is nonpleochroic. Kolskyite is triclinic, space group P1\uaf, a 5.387(1), b 7.091(1), c 15.473(3) \uc5, \u3b1 96.580(4), \u3b2 93.948(4), \u3b3 89.818(3)\ub0 , V 585.8(3) \uc53. The strongest lines in the X-ray powder-diffraction pattern [d(\uc5)(I)(hkl)] are: 15.161(100)(001), 2.810(19)(121, 12\uaf2), 3.069(12) (005), 2.938(10)((1\uaf2\uaf1,120, 12\uaf1), 2.680(9)((1\uaf2\uaf3 ,200,114, 2\uaf01), 1.771(9) (04\uaf1,040), 2.618(8)(12\uaf3,122), 2.062(7)(221,22\uaf2,2\uaf2\uaf3,2\uaf22), and 1.600(7)(3\uaf2\uaf1,3\uaf20,320). Chemical analysis by electron microprobe gave Nb2O5 6.96, ZrO2 0.12, TiO2 26.38, SiO2 27.08, FeO 0.83, MnO 2.95, MgO 0.76, BaO 3.20, SrO 5.21, CaO 4.41, K2O 0.79, Na2O 6.75, H2O 13.81, F 0.70, O = F -0.29, sum 99.66 wt.%; H2O was determined from structure solution and refinement. The empirical formula was calculated on 25 (O + F) apfu: (Na1.93 Mn0.04Ca0.03)\u3a32(Ca0.67Sr0.45Ba 0.19K0.15)\u3a31.46(Ti2.93Nb0.46Mn0.33Mg0.17Fe2+0.10Zr0.01)\u3a34Si4.00O24.67H13.60F0.33, Z = 1. Simplified and ideal formulae are as follows: (Ca,\u25a1)2Na2Ti4(Si2O7)2O4(H2O)7 and (Ca\u25a1)Na2Ti4(Si2O7)2O4(H2O)7. The FTIR spectrum of the mineral contains the following bands: 3c3300 cm-1 (very broad) and 3c1600 cm-1 (sharp). The crystal structure was solved by direct methods and refined to an R1 index of 8.8%. The crystal structure of kolskyite is a combination of a TS (titanium-silicate) block and an I (intermediate) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral). The TS block exhibits linkage and stereochemistry typical for Group IV [Ti (+ Mg + Mn) = 4 apfu] of Ti-disilicate minerals. In the H sheet in kolskyite, Si2O7 groups link to [6]-coordinated Ti octahedra. In the O sheet, Ti-dominant and Na octahedra each form brookite-like chains. There is one peripheral AP site occupied mainly by Ca (less Sr, Ba, and K) at 68%. The I block consists of H2O groups and AP atoms. The I block is topologically identical to those in the kazanskyite and nechelyustovite structures. The mineral is named after the Kola Peninsula (Kolskyi Poluostrov in Russian). The chemical formula and structure of kolskyite were predicted by Sokolova & C\ue1mara (2010); this is the first correct prediction of a TS-block mineral

Sveinbergeite, Ca(Fe 2+6 Fe 3+)Ti 2(Si 4O 12) 2O 2(OH) 5(H 2O) 4, a new astrophyllite-group mineral from the Larvik Plutonic Complex, Oslo Region, Norway : description and crystal structure

Sveinbergeite, Ca(Fe 2+6 Fe 3+)Ti 2(Si 4O 12) 2O 2(OH) 5(H 2O) 4, is a new astrophyllite-group mineral discovered in a syenite pegmatite at Buer on the Vester\uf8ya peninsula, Sandefjord, Oslo Region, Norway. The mineral occurs in pegmatite cavities as 0.01-0.05 mm thick lamellar (0.2-0.5 75-10 mm) crystals forming rosette-like divergent groups and spherical aggregates, which are covered by brown coatings of iron (and possibly manganese) oxides, associated with magnesiokatophorite, aegirine, microcline, albite, calcite, fluorapatite, molybdenite, galena and a hochelagaite-like mineral. Crystals of sveinbergeite are deep green with a pale green streak and a vitreous and pearly lustre. Sveinbergeite has perfect cleavage on 001 and a Mohs hardness of 3. Its calculated density is 3.152 g/cm 3. Itis biaxial positive with \u3b1 1.745(2), \u3b2 1.746(2), \u3b3 1.753(2), 2V(meas.) = 20(3)\ub0. The mineral is pleochroic according to the scheme Z > X 3c Y : Z is deep green, X and Y are brownish green Orientation is as follows: X \ (001), Y b = 12\ub0, Z = a, elongation positive. Sveinbergeite is triclinic, space group P1\u304 , a = 5.329(4), b = 11.803(8), c = 11.822(8) \ub0 \u3b1 = 101.140(8)\ub0, \u3b2 = 98.224(8)\ub0, \u3b3 = 102.442(8)\ub0; V = 699.0(8) \uc5 3; Z = 1. The nine strongest lines in the X-ray powder diffraction pattern [d in \uc5 (I)(hkl)] are: 11.395(100)(001,010), 2.880(38)(004), 2.640(31)(2\u30410,1\u30441), 1.643(24)(07\u304 1,07\u3042), 2.492(20)(21\u304 1), 1.616(15)(070), 1.573(14)(3\u304 2\u304 2), 2.270(13)(1\u304 3\u304 4) and 2.757(12)(1\u30440,1\u3043\u3042). Chemical analysis by electron microprobe gave Nb 2O 5 0.55, TiO 2 10.76, ZrO 2 0.48, SiO 2 34.41, Al 2O 3 0.34, Fe 2O 3 5.57, FeO 29.39, MnO 1.27, CaO 3.87, MgO 0.52, K 2O 0.49, Na 2O 0.27, F 0.24, H 2O 8.05, O=F 0.10, sum 96.11 wt.%, the amount of H 2O was determined from structure refinement, and the valence state of Fe was calculated from structure refinementin accord with M\uf6ssbauer spectroscopy. The empirical formula, calculated on the basis of eight(S i + Al) p.f.u., is (Ca 0.95Na 0.12K 0.14)S 1.21(Fe 2+5.65Fe 3+0.93Mn 0.25Mg 0.18)\u3c3 7.01(Ti 1.86Nb 0.06Zr 0.05Fe 3+0.03) \u3c3 2 (Si 7.91Al 0.09) \u3c3 8O 34.61H 12.34F 0.17, Z = 1. The infrared spectrum of the mineral contains the following absorption frequencies: 3588, 3c3398 (broad), 3c3204 (broad), 1628, 1069, 1009, 942, 702, 655 and 560 cm -1. The crystal structure of the mineral was solved by direct methods and refined to an R 1 index of 21.81%. The main structural unit in the sveinbergeite structure is an HOH layer which is topologically identical to that in the astrophyllite structure. Sveinbergeite differs from all other minerals of the astrophyllite group in the composition and topology of the interstitial A and B sites and linkage of adjacent HOH layers. The mineral is named in honour of Svein Arne Berge (b. 1949), a noted Norwegian amateur mineralogist and collector who was the first to observe and record this mineral from its type locality as a potential new species

Nafertisite, a layer titanosilicate member of a polysomatic series including mica

Nafertisite, (Na,K)3(Fe2+,Fe3+,\u25a1)10[Ti 2(Si,Fe3+,Al)12O37](OH,O) 6, is an alkaline titanosilicate from the Khibina massif (Kola Peninsula, Russia). It is monoclinic A2/m with a = 5.353(4), b = 16.176(12), c = 21.95(2) \uc5, f = 94.6(2)\ub0, Z = 2. The comparison with bafertisite, Ba2(Fe,Mn)4[Ti2Si4O 17](OH,O)3, and astrophyllite, (K,Na)3(Fe,Mn)7 [Ti2Si8O27](OH,O)4, allowed to obtain a structural model for nafertisite which has been tested against X-ray diffraction data obtained from a very poor crystal. On the basis of a bafertisite-like B module (A,\u25a1)2(M,\u25a1)4 [X2T4O17](OH)2 and a mica-like M module (A,\u25a1)(M,\u25a1)3[T4O10](OH)2, a polysomatic series BMn can be defined where bafertisite, astrophyllite, nafertisite and mica are the members with n = 0, 1, 2, 1e, respectively. It is called heterophyllosilicate series because the crystal structures of the members consist of 2:1 HOH layers where O is an octahedral sheet and H is a tetrahedral-like sheet which differs from the T sheet of the phyllosilicates for the insertion of Ti octahedra; these play a role similar to that of Si tetrahedra. A group of titanosilicates is shown to be derivatives of the bafertisite structure with different interlayer contents

Paraershovite, Na3K3Fe3+2(Si4O10OH)2(OH)2(H 2O)4, a new mineral species from the Khibina Alkaline Massif, Kola peninsula, Russia : description and crystal structure

Paraershovite,Na3K3Fe3+2(Si4O10OH)2(OH)2(H 2O)4, is a new silicate mineral species discovered in a hyperagpaitic pegmatite from Mount Yukspor, Khibina alkaline massif. Kola Peninsula, Russia. The mineral occurs as equant (100) platy and [001] elongate prismatic crystals up to 0.5-1 mm and aggregates up to 2-3 mm sporadically scattered in a pegmatite matrix. Associated minerals are sodalite, aegirine, arfvedsonite, pectolite, shcherbakovite, lamprophyllite, lomonosovite, shafranovskite, villiaumite and natrophosphate. Crystals of paraershovite are yellow with orange or pinkish shades, with a white streak and vitreous luster. The mineral is translucent or transparent, and non-fluorescent under 240-400 nm ultraviolet radiation. Paraershovite has a perfect 100 cleavage. It is brittle, has a step-like and splintery fracture, and a Mohs hardness of 3. Its observed and calculated densities (g/cm3) are 2.60(3) (by microvolumetric methods) and 2.584 (using the empirical formula), respectively. It is biaxial positive, with \u3b1 1.569(2), \u3b2 1.583(2), 7\u3b3 1.602(2), 2V(meas.) = 80(3)7deg;, 2V(calc.) = 82\ub0, non-pleochroic, dispersion r > \u3bd (weak), with X \u39b c = 84\ub0, Y \u39b c = 66\ub0, Z \u3bb c = 24\ub0. Paraershovite is triclinic, space group P1\u304, a 10.1978(5), b 12.0155(6), c 5.2263(3) \uc5, \u3b1 103.439(1), \u3b2 96.020(1), \u3b3 91.683(1)\ub0, V618.46(3J \uc53, Z = 1. The strongest lines in the X-ray powderniiffraction pattern [d in A(I)(AW)] are: 11.778(100)(010), 4.390(70)( 11\u3041, 02\u3041), 3.012(70)(230, 3\u30420), 2.606(70)(32\u3041,131,012,11\u3042), 4.109(60)(1\u30411 ,12\u3041) and 2.730(60)(32\u3041,14\u3041,14\u3041,31\u3041,221). A chemical analysis with an electron microprobe gave Na20 7.77, MgO0.24, Si02 49.67, Al2O30.58, K20 14.07, Fe203 11.29, MnO 0.73,Ti02 3.32, F0.39, H20 10.98,0 = F-0.16, sum 98.88 wt.%; the valence state of Fe was determined by M\uf6ssbauer spectroscopy, and the amount of H20 was calculated from the crystal-structure refinement. The empirical formula based on 28 anions is (Na2.44\u25a1156)\u3c34K 2.91 (Fe3+1.38Ti0.40Al 0.11Mn2+0.10Mgi0.06) 112.05Si8.05O20 [(OH)3.80 F 0.20] 114(H2O)4. The IR spectrum of the mineral has absorption bands at 1600 and 3500 cm-1, showing the presence of H2O and OH groups in the stnicture. The crystal structure of paraershovite was solved by direct methods and refined to an R1 index of 4.28% (for 2134 observed [Fo>4\u3c3F] unique reflections measured with MoK\u3b1 radiation on a Bruker P4 diffractometer with a CCD 4K APEX detector). The crystal structure of paraershovite is isostructural with that of ershovite, ideally Na4K 3(Fe2+,Mn,Ti)2 (Si4O 10OH)2(OH)2(H2O)4 (a 10.244, b 11.924, c 5.276 \uc5, \u3b1 103.491, \u3b2 96.960, \u3b3 91.945\ub0, V 620.8 \uc53, space group P\u12b). Paraershovite is a Na-deficient, Fe3+-dominant analogue of ershovite. It can be considered an oxidized product of the epithermal alteration of ershovite. Paraershovite is chemically related to ershovite by the heterovalent substitution \u25a1 + Fe23+ \u2192 Na++M 22.5+, where M2.5+ represents Fe2+, Mn2+ and Ti4+. The name paraershovite, derived from the Greek para (close by) and ershovite, recalls the close structural, chemical and genetic relations between paraershovite and ershovite