ALBERT

Description: Bosiite, NaFe 3+ 3 (Al 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, is a new mineral species of the tourmaline supergroup from the Darasun gold deposit (Darasun mine), Vershino-Darasunskiy, Transbaikal Krai, Eastern-Siberian Region, Russia (52°20'24''N, 115°29'23''E). Bosiite formed as a hydrothermal phase in a gold-bearing quartz-vein spatially related to the Amudzhikan–Sretensky subvolcanic K-rich granodiorite-porphyry intrusion. Ores of this deposit are enriched in sulfides (up to 60%). Bosiite is intimately associated with other tourmalines. The first tourmaline generation is bosiite, which is followed by a second generation of oxy-dravite and a third generation of dravite. Bosiite also coexists with quartz and pyrite; further associated minerals in the vein are gangue minerals (quartz, calcite, and dolomite), sulfides (pyrite, arsenopyrite, chalcopyrite, pyrrhotite, tetrahedrite, sphalerite, and galena) and native gold. Crystals of bosiite are dark brown to black with a pale-brown streak. Bosiite is brittle and has a Mohs hardness of 7; it is non-fluorescent, has no observable parting and cleavage. It has a measured density of 3.23(3) g/cm 3 (by pycnometry) and a calculated density of 3.26(1) g/cm 3 . In plane-polarized light, it is pleochroic, O = yellow-brown, E = red-brown. Bosiite is uniaxial negative, = 1.760(5), = 1.687(5). The mineral is trigonal, space group R 3 m , a = 16.101(3), c = 7.327(2) Å, V = 1645.0(6) Å 3 . The eight strongest X-ray diffraction lines in the (calculated) powder pattern [ d in Å( I ) hkl ] are: 2.606(100)(50-1), 8.051(58)(100), 3.008(58)(3-1-2), 4.025(57)(4-20), 3.543(50)(10-2), 4.279(46) (3-11), 2.068(45)(6-1-2), 4.648(28)(300). Analysis by a combination of electron microprobe (EMPA), inductively coupled plasma mass spectrometry (ICP-MS), Mössbauer spectroscopic data and crystal-structure refinement results in the empirical structural formula: \[ \begin{array}{c}{}^{X}{\left({\mathrm{Na}}_{0.73}{\mathrm{Ca}}_{0.23}{\square }_{0.04}\right)}_{\mathrm{\Sigma }1.00}{}^{Y}{\left({\mathrm{Fe}}^{3+}{}_{1.47}{\mathrm{Mg}}_{0.80}{\mathrm{Fe}}^{2+}{}_{0.59}{\mathrm{Al}}_{0.13}{\mathrm{Ti}}^{4+}{}_{0.01}\right)}_{\mathrm{\Sigma }3.00}{}^{Z}{\left({\mathrm{Al}}_{3.23}{\mathrm{Fe}}^{3+}{}_{1.88}{\mathrm{Mg}}_{0.89}\right)}_{\mathrm{\Sigma }6.00}\\\relax {}^{T}{\left({\mathrm{Si}}_{5.92}{\mathrm{Al}}_{0.08}{\mathrm{O}}_{18}\right)}_{\mathrm{\Sigma }6.00}{\left({\mathrm{BO}}_{3}\right)}_{3}{}^{V}{\left(\mathrm{OH}\right)}_{3}{}^{W}{\left[{\mathrm{O}}_{0.85}{\left(\mathrm{OH}\right)}_{0.15}\right]}_{\mathrm{\Sigma }1.00}\end{array} \] According to the IMA-CNMNC guidelines, the dominant valence at the Y site is 3+ and the dominant cation is Fe 3+ . To accommodate the disorder and allocating cations to the Z and Y sites, the recommended procedure leads to the optimized empirical formula (based on 31 O): X (Na 0.73 Ca 0.23 0.04 ) Y (Fe 3+ 2.40 Fe 2+ 0.59 Ti 4+ 0.01 ) Z (Al 3.36 Mg 1.69 Fe 3+ 0.95 ) T (Si 5.92 Al 0.08 O 18 ) (BO 3 ) 3 V (OH) 3 W [O 0.85 (OH) 0.15 ]. Bosiite, ideally NaFe 3+ 3 (Al 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, is related to end-member povondraite, ideally NaFe 3+ 3 (Fe 3+ 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, by the substitution Z Al 4 -〉 Z Fe 3+ 4 . Further, bosiite is related to oxy-dravite, ideally Na(Al 2 Mg)(Al 5 Mg)(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, by the substitutions [6] Fe 3+ 3 -〉 [6] Al 3 . Bosiite is named after Dr. Ferdinando Bosi, researcher at the University of Rome La Sapienza, Italy, and an expert on the crystallography and mineralogy of the tourmaline-supergroup minerals and the spinels.

Description: A monoclinic (2 M ) polytype of sideronatrite, Na 2 Fe(SO 4 ) 2 (OH)(H 2 O) 3 , was found at Xitieshan, Qinghai Province, China. The crystal structure was solved by direct methods and refined by full-matrix least-squares ( R 1 = 3.88 %) in the space group P 12 1 / n 1 with a = 7.1559(14), b = 7.2845(15), c = 20.889(4) Å, β = 99.37(3)°, V = 1074.4(4) Å 3 , and Z = 4, using 2207 observed reflections with I 〉 2( I ). The atomic arrangement of sideronatrite-2 M confirms a theoretical model in space group P 2 1 / a , previously proposed in literature. The structure of sideronatrite-2 M is based on ferric-sulfate chains of 7 Å periodicity, similar to those observed in the structures of the orthorhombic polytype and of metasideronatrite. The system of hydrogen bonds has been determined.

Description: 〈span〉The crystal structures of coquimbite and paracoquimbite from the Hongshan Cu–Au deposit, NW China, were refined by single-crystal X-ray diffraction, including the positions of all non-H atoms and hydrogen atoms.The unit-cell parameters of coquimbite are 〈span〉a〈/span〉 = 10.9644(15), 〈span〉c〈/span〉 = 17.090(3) Å, and 〈span〉V〈/span〉 = 1769.6(5) Å〈sup〉3〈/sup〉, 〈span〉Z〈/span〉 = 4 with space group 〈span〉P〈/span〉3¯1〈span〉c〈/span〉. The crystal structure was refined based on 1352 unique reflections to 〈span〉R〈/span〉1(〈span〉F〈/span〉) = 0.0301, yielding the formula Fe〈sub〉1.64〈/sub〉Al〈sub〉0.36〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉3〈/sub〉∙9H〈sub〉2〈/sub〉O. Among the three cation positions of coquimbite, the isolated octahedral one is dominantly occupied by Al, 〈span〉i.e.〈/span〉 Al〈sub〉0.660(3)〈/sub〉Fe〈sub〉0.340(3)〈/sub〉. Consequently, the average Al–O interatomic distance is 1.9155 Å, smaller than the Fe–O distances, 2.002 Å for Fe(1), and 1.989 Å for Fe(2). Based on the structure data available for coquimbite in the literature, the ideal formula should be expressed as AlFe〈sub〉3〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉6〈/sub〉·18H〈sub〉2〈/sub〉O (〈span〉Z〈/span〉 = 2) or Fe〈sub〉2−〈span〉x〈/span〉〈/sub〉Al〈sub〉〈span〉x〈/span〉〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉3〈/sub〉·9H〈sub〉2〈/sub〉O, 〈span〉x〈/span〉 ∼ 0.5 rather than Fe〈sup〉3+〈/sup〉〈sub〉2〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉3〈/sub〉∙9H〈sub〉2〈/sub〉O. The simplified formula for coquimbite from Hongshan is (Al〈sub〉0.66〈/sub〉Fe〈sub〉0.34〈/sub〉)Fe〈sub〉3〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉6〈/sub〉·18H〈sub〉2〈/sub〉O.The unit-cell parameters of paracoquimbite are 〈span〉a〈/span〉 = 10.9631(16), 〈span〉c〈/span〉 = 51.473(10) Å, and 〈span〉V〈/span〉 = 5357.7(15) Å〈sup〉3〈/sup〉, 〈span〉Z〈/span〉 = 12 with space group 〈span〉R〈/span〉3¯. The crystal structure was refined using 2733 unique reflections to 〈span〉R〈/span〉1(〈span〉F〈/span〉) = 0.0550, which led to the formula Fe〈sub〉1.91〈/sub〉Al〈sub〉0.09〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉3〈/sub〉∙9H〈sub〉2〈/sub〉O. There are five non-equivalent octahedrally coordinated metal sites for Fe in the structure of paracoquimbite. The range of Fe〈sup〉[6]〈/sup〉–O interatomic distances in paracoquimbite (1.966 Å–2.016 Å) can well be compared with those found in various sulfate minerals of ferric iron.Both minerals are characterized by a complex system of hydrogen bonds involving three types of H〈sub〉2〈/sub〉O molecules, respectively: those of [Fe〈sub〉3〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉6〈/sub〉(H〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉]〈sup〉3−〈/sup〉 clusters, of isolated [Fe(H〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉]〈sup〉3+〈/sup〉 or [Al(H〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉]〈sup〉3+〈/sup〉 octahedra and further interstitial (H〈sub〉2〈/sub〉O) groups. The interstitial H〈sub〉2〈/sub〉O molecules resemble a cyclohexane-like chair and are held in the structure solely by hydrogen bonding. In coquimbite H〈sub〉2〈/sub〉O〈sub〉W〈/sub〉(2) is disordered with two alternative orientations (H2B1 and H2B2), in paracoquimbite interstitial H〈sub〉2〈/sub〉O consists of two H〈sub〉2〈/sub〉O molecules, H〈sub〉2〈/sub〉O〈sub〉W〈/sub〉(3) and H〈sub〉2〈/sub〉O〈sub〉W〈/sub〉(4). The range of the O–H stretching frequencies between ∼2750 and ∼3650 cm〈sup〉−1〈/sup〉 from infrared spectroscopy for paracoquimbite is in fair accordance with the calculated values between ∼2874 and ∼3600 cm〈sup〉−1〈/sup〉 from both the 〈span〉d〈/span〉(O…O) lengths and the 〈span〉d〈/span〉(H…O) lengths.〈/span〉

Description: Cairncrossite is a new phyllosilicate species found in manganese ore on dumps of the Wessels Mine, Kalahari Manganese Field, South Africa. Associated minerals are richterite, sugilite, lizardite and fibrous pectolite. It occurs as radiating platy micaceous aggregates of up to 1 cm in size. Cairncrossite is colourless, appearing white, and the crystals are translucent to transparent with a white streak and vitreous to pearly lustre. The crystals are sectile before brittle fracture, with a Mohs hardness of 3. A perfect cleavage parallel (001) is observed. The calculated density is 2.486 g cm –3 . The mineral is biaxial positive with n α = 1.518(2), n β = 1.522(2), n = 1.546(2), 2 V obs = 33.9(6)° (2 V calc = 44.97°) at 589.3 nm and 24°C. The orientation of the indicatrix is Z ^ c * = 10°. The dispersion is weak ( r 〈 v ) and no pleochroism is observed. An intense light-blue fluorescence is emitted under shortwave UV radiation. Cairncrossite is triclinic, space group P $$\overline{1}$$ , a = 9.6265(5), b = 9.6391(5), c = 15.6534(10) Å, α = 100.89(1), β = 91.27(1), = 119.73(1)°, V = 1227.08(13) Å 3 , Z = 1. The strongest lines in the Gandolfi X-ray powder-diffraction pattern [ d in Å( I )( hkl )] are 15.230 (100)(001), 8.290 (15)(1–10), 5.080(25)(003), 3.807(30)(004), and 3.045(20)(005). The chemical composition obtained by electron-microprobe analysis is Na 2 O 3.06, K 2 O 0.11, CaO 18.61, SiO 2 54.91, SrO 11.75, total 88.44 wt%. The relevant empirical formula, based on 16 Si atoms per formula unit ( apfu ) and TGA data is: Sr 1.99 K 0.02 Ca 5.81 Na 1.73 Si 16 O 55.84 H 30.33 . Taking variable sodium contents into account, the idealized structural formula is Sr 2 Ca 7–x Na 2x (Si 4 O 10 ) 4 (OH) 2 (H 2 O) 15–x with 0 ≤ x ≤ 1, and the simplified formula for sodium-rich crystals is SrCa 3 Na(Si 4 O 10 ) 2 (OH)(H 2 O) 7 with Z = 2. The structure of cairncrossite was refined on single-crystal X-ray data (Mo K α radiation) to R 1 = 0.047. Cairncrossite belongs to the gyrolite and reyerite mineral groups, it is characterized by sheets consisting of edge-sharing CaO 6 octahedra, which are corner-linked on both sides to silicate layers. These units are intercalated by layers formed by SrO 8 polyhedra, which are arranged in pairs via a common edge, and further bound to disordered NaO 6 polyhedra. A complex system of hydrogen bonds strengthens the linkage to adjacent silicate layers. Cairncrossite exhibits a two-phase endothermic weight loss of the H 2 O molecules in the range 25–400°C; however, the mineral shows a nearly complete rehydration capability up to 400°C. The new mineral is named in honour of Bruce Cairncross, Professor and Head of the Department of Geology, University of Johannesburg.

Description: The crystal structures of the secondary ferric iron minerals kamarizaite, Fe 3 3+ (AsO 4 ) 2 (OH) 3 · 3H 2 O, and tinticite, Fe 3 3+ (PO 4 ) 2 (OH) 3 · 3H 2 O, for which highly contradictory data on crystal symmetry were reported, were studied by a combination of single-crystal X-ray diffraction and Rietveld refinement (supplemented by chemical analyses and thermogravimetry), using type material of both species and additional samples from several other localities, including the type localities. The previously unknown crystal structure of kamarizaite was determined from single-crystal intensity data (Mo K α, 293 K, R ( F ) = 2.91 %; all H atoms detected) using a sample from the Le Mazet vein, Échassières, Auvergne, France. The mineral is triclinic, space group $$P\overline{1}$$ (no. 2), with a = 7.671(2), b = 8.040(2), c = 10.180(2) Å, α = 68.31(3), β = 75.35(3), = 63.52(3)°, V = 519.3(2) Å 3 , Z = 2. Rietveld analyses of fine-grained kamarizaite collected underground at two different spots in Lavrion, Greece (Hilarion and Jean Baptiste areas) confirmed the structure model. Rietveld analyses of fine-grained tinticite from Tintic, Utah (USA), Bruguers (Spain) and Weckersdorf (Germany) demonstrate that kamarizaite and tinticite are triclinic and isotypic. A previously published structure model for tinticite, as well as the originally reported orthorhombic symmetry for kamarizaite, are shown to be incorrect. Refined unit-cell parameters of a cotype tinticite specimen from Tintic are: a = 7.647(1), b = 7.958(1), c = 9.987(1) Å, α = 67.90(1), β = 76.10(1), = 64.10(1)°, V = 504.4(2) Å 3 . Bruguers and Weckersdorf tinticite have very similar parameters. The common atomic arrangement is characterised by three unique, octahedrally coordinated Fe sites (on which Fe may be partially replaced by minor Al), two unique tetrahedrally coordinated T (As or P) sites, eight O, three O h , three O w and nine H sites. The topology features zig-zag chains along $$\left[\overline{1}10\right]$$ of dimers built of two edge-sharing FeO 6 octahedra corner-linked by a third FeO 6 octahedron. The chains are corner-linked by the T O 4 tetrahedra thus establishing a mixed octahedral-tetrahedral framework with a T :Fe ratio of 0.67, a pronounced layered arrangement parallel to (001) and narrow channels along [010]. Medium-strong to weak hydrogen-bonds provide additional strengthening of the structure. The topology is closely related to that of the recently described, triclinic aluminium phosphate afmite.

Description: The new mineral calciomurmanite, (Na,) 2 Ca(Ti,Mg,Nb) 4 [Si 2 O 7 ] 2 O 2 (OH,O) 2 (H 2 O) 4 , a Na-Ca ordered analogue of murmanite, was found in three localities at Kola Peninsula, Russia: at Mt. Flora in the Lovozero alkaline complex (the holotype) and at Mts. Eveslogchorr (the cotype) and Koashva, both in the Khibiny alkaline complex. Calciomurmanite is a hydrothermal mineral formed as a result of late-stage, low-temperature alteration (hydration combined with natural cation exchange) of a high-temperature, anhydrous phosphate-bearing titanosilicate, most likely lomonosovite and/or betalomonosovite, in the peralkaline (hyperagpaitic) rocks. The holotype sample is associated with microcline, aegirine, lorenzenite and fluorapatite, whereas the cotype sample occurs with microcline, aegirine, lamprophyllite, tsepinite-Ca and tsepinite-K. The mineral occurs as lamellae up to 0.1 x 0.4 x 0.6 cm, sometimes combined in fan-shaped aggregates up to 3.5 cm. Calciomurmanite is pale brownish or purple; the streak is white. The lustre is nacreous on cleavage surface and greasy on broken surface across cleavage. The (001) cleavage is perfect, mica-like; the fracture is stepped. D meas = 2.70(3), D calc = 2.85 g cm –3 . The mineral is optically biaxial (–), α = 1.680(4), β = 1.728(4), = 1.743(4), 2 V meas = 58(5)°. The IR spectrum is reported. The chemical composition (wt%, electron-microprobe data, H 2 O by the Alimarin method) is: Na 2 O 5.39, K 2 O 0.30, CaO 7.61, MgO 2.54, MnO 2.65, FeO 1.93, Al 2 O 3 0.85, SiO 2 30.27, TiO 2 29.69, Nb 2 O 5 6.14, P 2 O 5 0.27, H 2 O 11.59, total 99.23. The empirical formula of the holotype sample, calculated on the basis of Si + Al = 4 apfu , is: Na 1.34 Ca 1.04 K 0.05 Mg 0.49 Mn 0.29 Fe 0.21 Nb 0.36 Ti 2.85 (Si 3.87 Al 0.13 ) 4 O 16.40 (OH) 1.60 (PO 4 ) 0.03 (H 2 O) 4.94 . Calciomurmanite is triclinic, P -1, a = 5.3470(6), b = 7.0774(7), c = 12.146(1) Å, α = 91.827(4), β = 107.527(4), = 90.155(4)°, V = 438.03(8) Å 3 and Z = 1. The strongest reflections of the X-ray powder pattern [ d ,Å( I )( hkl )] are: 11.69(100)(001), 5.87(68)(011, 002), 4.25(89) (–1–11, –111), 3.825(44)(–1–12, 003, –112), 2.940(100)(–1–21, –121), 2.900(79)(004, 120). The crystal structure was solved by direct methods from single-crystal low-temperature (200 K) X-ray diffraction data and refined to R = 0.0656 for the holotype and 0.0663 for the cotype. The structure is based on a three-sheet HOH block: an octahedral ( O ) sheet containing alternating chains of NaO 6 and TiO 6 octahedra and two heteropolyhedral ( H ) sheets consisting of Si 2 O 7 groups, TiO 6 octahedra and CaO 8 polyhedra. H 2 O molecules occupy two sites in the interlayer space.

Description: The crystal structure of vigrishinite, an epistolite-group heterophyllosilicate with essential Zn, has been reinvestigated; the ideal end-member formula is revised to Zn 2 Ti 4– x (Si 2 O 7 ) 2 O 2 (OH,F,O) 2 (H 2 O,OH,) 4 with x 〈1. Structure models of Zn-exchanged forms of murmanite after 5 and 24 hour experiments with 1N ZnSO 4 solution at 90 °C have been obtained from single-crystal X-ray diffraction data. The structural formulae are [ B 1] Ca 0.04 {Na 1.22 (Ti 1.19 Mn 0.60 Nb 0.21 )}{ [ A 1, A 2] Zn 1.03 (Ti 1.64 Nb 0.36 )[Si 2 O 7 ] 2 }O 2 (O,OH) 2 (H 2 O) 4 for vigrishinite and {Na 1.14 (Ti 1.45 Mn 0.50 Nb 0.05 )}{ [A1] Ca 0.77 [A2] Zn 0.13 (Ti 1.85 Nb 0.15 )[Si 2 O 7 ] 2 }O 2 (OH,O) 2 (H 2 O) 4 and [ B 1] Zn 0.15 [ B 2] Ca 0.18 {Na 1.06 (Ti 1.32 Mn 0.60 Nb 0.08 )}{ [A1] Zn 0.70 [A2] Ca 0.12 (Ti 1.74 Nb 0.26 )[Si 2 O 7 ] 2 }O 2 (OH,O) 2 (H 2 O) 4 for the 5 and 24 hour Zn-exchanged forms of murmanite, respectively (braces give successively the contents of the octahedral O and heteropolyhedral H sheets). The triclinic ( P –1) unit-cell parameters are respectively: a = 8.7127(17), 8.871(3), 8.748(2) Å; b =8.6823(17), 8.844(6), 8.724(2) Å; c = 11.746(2), 11.734(6), 11.675(3) Å; α = 91.481(4), 92.75(3), 92.503(13)°; β = 98.471(4), 97.60(4), 97.846(13)°; = 105.474(4), 106.23(2), 105.875(13)°; V = 845.0(3), 872.7(8), 845.9(4) Å 3 . Our data (1) confirm that vigrishinite was formed as a result of natural ion-exchange of murmanite Na 4 Ti 4 (Si 2 O 7 ) 2 O 4 · 4H 2 O with Zn 2+ in low-temperature solutions; (2) prove that direct transformation of lomonosovite Na 4 Ti 4 (Si 2 O 7 ) 2 O 4 · 2Na 3 PO 4 into vigrishinite, without prior leaching of Na + and PO 4 3– from the former and formation of murmanite, is unlikely; (3) suggest the following ion-exchange mechanism: during the early stage Na + leaches into the solution whereas Ca 2+ , a common admixture in murmanite, migrates into one of the sites in the H sheet, leaving another site vacant for further entry of Zn; in the next stage Zn 2+ enters the emptied site in the H sheet and, in small amount, into the interlayer whereas Ca 2+ partly moves from the H sheet into the interlayer; (4) show the transformation of the murmanite-type unit cell ( P –1; V 440 Å3) into the vigrishinite-type cell with a and b parameters corresponding to the ab face diagonals of the former during the first stage of the exchange with Zn, due to ordering in the H sheet. New findings of vigrishinite in two pegmatites of the Lovozero massif, Kola peninsula, Russia (at Severnyi open pit, Mt. Alluaiv and at Pegmatite #60, Mt. Karnasurt) in the same setting as at the type locality, i.e . only in close contact with cavities after dissolved sphalerite, show that the ion exchange in epistolite-group heterophyllosilicates is not uncommon in Nature. Our data indicate there is a continuous solid solution between murmanite and vigrishinite.

Description: 〈span〉A detailed investigation was conducted on high-pressure (~1.4 GPa) tourmaline from an Eoalpine mafic eclogite, which occurs in the Kreuzeck Mountains, Eastern Alps, Austria. Tourmaline from this locality contains the highest amount of Sr〈sup〉2+〈/sup〉 (up to 0.68 wt% SrO) known to date. The space group is 〈span〉R〈/span〉3〈span〉m〈/span〉 with unit-cell parameters 〈span〉a〈/span〉 = 15.944(1), 〈span〉c〈/span〉 = 7.202(1) Å, 〈span〉V〈/span〉 = 1585.5(3) Å〈sup〉3〈/sup〉. Analyses by a combination of electron microprobe, optical absorption spectroscopy and crystal-structure refinement (〈span〉R〈/span〉1 = 1.31%) result in the structural formula 〈sup〉〈span〉X〈/span〉〈/sup〉(Na〈sub〉0.85〈/sub〉Ca〈sub〉0.08〈/sub〉Sr〈sub〉0.06〈/sub〉K〈sub〉0.01〈/sub〉)〈sub〉Σ1.00〈/sub〉〈sup〉〈span〉Y〈/span〉〈/sup〉(Mg〈sub〉1.68〈/sub〉Al〈sub〉0.70〈/sub〉Fe0.373+Ti0.104+Fe0.112+Ca〈sub〉0.03〈/sub〉Cr0.013+)〈sub〉Σ3.00〈/sub〉〈sup〉〈span〉Z〈/span〉〈/sup〉(Al〈sub〉5.15〈/sub〉Mg〈sub〉0.80〈/sub〉Fe0.053+)〈sub〉Σ6.00〈/sub〉〈sup〉〈span〉T〈/span〉〈/sup〉(Si〈sub〉5.82〈/sub〉B〈sub〉0.10〈/sub〉Al〈sub〉0.08〈/sub〉O〈sub〉18〈/sub〉) (BO〈sub〉3〈/sub〉)〈sub〉3〈/sub〉〈sup〉〈span〉V〈/span〉〈/sup〉(OH)〈sub〉3〈/sub〉〈sup〉〈span〉W〈/span〉〈/sup〉[O〈sub〉0.45〈/sub〉(OH)〈sub〉0.35〈/sub〉F〈sub〉0.20〈/sub〉]. The 〈span〉T〈/span〉 site contains mainly Si and additionally small amounts of B and Al. According to optical absorption spectroscopy (using the band near 1120 nm), the Fe〈sup〉3+〈/sup〉/Fe ratio is 79 ± 2%, suggesting that this high-pressure tourmaline crystallized under oxidizing conditions. It has a significant oxy-dravite component. A near-rim zone contains 0.6 wt% Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, 0.5 wt% PbO〈sub〉2〈/sub〉, 0.2 wt% NiO and 0.1 wt% V〈sub〉2〈/sub〉O〈sub〉3〈/sub〉. Only a small F content was found by structure refinement. There is no evidence for significant 〈span〉X〈/span〉-site vacancy in the investigated tourmaline zones. We assume that the original boron source for tourmaline crystallization in the eclogite, 〈span〉i.e.〈/span〉 tourmaline-bearing pegmatites in the country-rock, were influenced by a Sr-bearing marble.〈/span〉

Description: The crystal structure of amarillite, NaFe(SO 4 ) 2 (H 2 O) 6 , was redetermined from a single crystal from Xitieshan, Qinghai Province, China. In complement to previous work, all non-H atoms were refined with anisotropic displacement parameters and H-atoms were located by difference Fourier methods and refined from X-ray diffraction data. The structure can be formally described by octahedral–tetrahedral "sheets" of corner-sharing [NaO 4 (H 2 O) 2 ] octahedra and (SO 4 ) tetrahedra, which constitute a structural sheet with composition [Na(SO 4 ) 2 (H 2 O) 2 ] 3– extending parallel to (001). The resultant sheets are held together by interstitial Fe 3+ cations and hydrogen bonds. The [NaO 4 (H 2 O) 2 ] octahedra donate four hydrogen bonds to the oxygen atoms of neighboring (SO 4 ) tetrahedra, thus strengthening connections in three dimensions. The interstitial [FeO 2 (H 2 O) 4 ] octahedra are linked by eight hydrogen bonds to the vertices of the adjacent octahedral–tetrahedral sheets, further stabilizing the crystal structure of amarillite. The FTIR spectrum of amarillite shows a strong absorption between 3000 cm –1 and 3500 cm –1 with maxima at ~3110cm –1 and ~3442 cm –1 , which is in accordance with the O–H···O distances derived from structure data.