Biachellaite, (Na,Ca,K)8(Si6Al6O24)(SO4)2(OH)0.5 · H2O, a new mineral species of the cancrinite group

Biachellaite, a new mineral species of the cancrinite group, has been found in a volcanic ejecta in the Biachella Valley, Sacrofano Caldera, Latium region, Italy, as colorless isometric hexagonal bipyramidal-pinacoidal crystals up to 1 cm in size overgrowing the walls of cavities in a rock sample composed of sanidine, diopside, andradite, leucite and hauyne. The mineral is brittle, with perfect cleavage parallel to {10$ \bar 1 $ \bar 1 0} and imperfect cleavage or parting (?) parallel to {0001}. The Mohs hardness is 5. D_meas = 2.51(1) g/cm³ (by equilibration with heavy liquids). The densities calculated from single-crystal X-ray data and from X-ray powder data are 2.515 g/cm³ and 2.520 g/cm³, respectively. The IR spectrum demonstrates the presence of SO₄²⁻, H₂O, and absence of CO₃²⁻. Biachellaite is uniaxial, positive, ω = 1.512(1), ɛ = 1.514(1). The weight loss on ignition (vacuum, 800°C, 1 h) is 1.6(1)%. The chemical composition determined by electron microprobe is as follows, wt %: 10.06 Na₂O, 5.85 K₂O, 12.13 CaO, 26.17 Al₂O₃, 31.46 SiO₂, 12.71 SO₃, 0.45 Cl, 1.6 H₂O (by TG data), −0.10 −O=Cl₂, total is 100.33. The empirical formula (Z = 15) is (Na_3.76Ca_2.50K_1.44)_Σ7.70(Si_6.06Al_5.94O₂₄)(SO₄)_1.84Cl_0.15(OH)_0.43 · 0.81H₂O. The simplified formula is as follows: (Na,Ca,K)₈(Si₆Al₆O₂₄)(SO₄)₂(OH)_0.5 · H₂O. Biachellaite is trigonal, space group P3, a =12.913(1), c = 79.605(5) ?; V = 11495(1) ?³. The crystal structure of biachellaite is characterized by the 30-layer stacking sequence (ABCABCACACBACBACBCACBACBACBABC)_∞. The tetrahedral framework contains three types of channels composed of cages of four varieties: cancrinite, sodalite, bystrite (losod) and liottite. The strongest lines of the X-ray powder diffraction pattern [d, ? (I, %) (hkl)] are as follows: 11.07 (19) (100, 101), 6.45 (18) (110, 111), 3.720 (100) (2.1.10, 300, 301, 2.0.16, 302), 3.576 (18) (1.0.21, 2.0.17, 306), 3.300 (47) (1.0.23, 2.1.15), 3.220 (16) (2.1.16, 222). The type material of biachellaite has been deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, registration number 3642/1.     

Alloriite, Na5K1.5Ca(Si6Al6O24)(SO4)(OH)0.5 · H2O, a new mineral species of the cancrinite group

Alloriite, a new mineral species, has been found in volcanic ejecta at Mt. Cavalluccio (Campagnano municipality, Roma province, Latium region, Italy) together with sanidine, biotite, andradite, and apatite. The mineral is named in honor of Roberto Allori (b. 1933), an amateur mineralogist and prominent mineral collector who carried out extensive and detailed field mineralogical investigations of volcanoes in the Latium region. Alloriite occurs as short prismatic and tabular crystals up to 1.5 × 2 mm in size. The mineral is colorless, transparent, with a white streak and vitreous luster. Alloriite is not fluorescent and brittle; the Mohs’ hardness is 5. The cleavage is imperfect parallel to {10 0}. The density measured with equilibration in heavy liquids is 2.35g/cm³ and calculated density (D _calc) is 2.358 g/cm³ (on the basis of X-ray single-crystal data) and 2.333 g/cm³ (from X-ray powder data). Alloriite is optically uniaxial, positive, ω = 1.497(2), and ɛ = 1.499(2). The infrared spectrum is given. The chemical composition (electron microprobe, H₂O determined using the Penfield method, CO₂, with selective sorption, wt %) is: 13.55 Na₂O, 6.67 K₂O, 6.23 CaO, 26.45 Al₂O₃, 34.64 SiO₂, 8.92 SO₃, 0.37 Cl, 2.1 H₂O, 0.7 CO₂, 0.08-O = Cl₂, where the total is 99.55. The empirical formula (Z = 1) is Na_19.16K_6.21Ca_4.87(Si_25.26Al_22.74O₉₆)(SO₄)_4.88(CO₃)_0.70Cl_0.46(OH)_0.76 · 4.73H₂O. The simplified formula (taking into account the structural data, Z = 4) is: [Na(H₂O)][Na₄K_1.5(SO₄)] · [Ca(OH,Cl)_0.5](Si₆Al₆O₂₄). The crystal structure has been studied (R = 0.052). Alloriite is trigonal, the space group is P31c; the unit-cell dimensions are a = 12.892(3), c = 21.340(5) ?, and V = 3071.6(15) ?³. The crystal structure of alloriite is based on the same tetrahedral framework as that of afghanite. In contrast to afghanite containing clusters [Ca-Cl]⁺ and chains ...Ca-Cl-Ca-Cl..., the new mineral contains clusters [Na-H₂O]⁺ and chains ...Na-H₂O-Na-H₂O.... The strongest reflections in the X-ray powder diffraction pattern [d, ? (I, %)(hkl)] are: 11.3(70)(100), 4.85(90)(104), 3.76(80)(300), 3.68(70)(301), 3.33(100)(214), and 2.694(70)(314, 008). The type material of alloriite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow. The registration number is 3459/1. Original Russian Text ? N.V. Chukanov, R.K. Rastsvetaeva, I.V. Pekov, A.E. Zadov, 2007, published in Zapiski Rossiiskogo Mineralogicheskogo Obshchestva, 2007, No. 1, pp. 82–89. A new mineral alloriite and its name were accepted by the Commission on New Minerals and Mineral Names, Russian Mineralogical Society, May 8, 2006. Approved by the Commission on New Minerals and Mineral Names, International Mineralogical Association, August 2, 2006.     

Synthesis, crystal structure and crystal chemistry of ferri-clinoholmquistite, ?Li 2Mg 3Fe 3+ 2Si 8O 22(OH) 2

This work reports the synthesis of ferri-clinoholmquistite, nominally _Li2(Mg₃Fe³⁺₂)Si₈O₂₂(OH)₂, at varying f_O2 conditions. Amphibole compositions were characterized by X-ray (powder and single-crystal) diffraction, microchemical (EMPA) and spectroscopic (FTIR, Mössbauer and Raman) techniques. Under reducing conditions ( NNO+1, where NNO = Nickel–Nickel oxide buffer), the amphibole yield is very high (>90%), but its composition, and in particular the FeO/Fe₂O₃ ratio, departs significantly from the nominal one. Under oxidizing conditions ( NNO+1.5), the amphibole yield is much lower (<60%, with Li-pyroxene abundant), but its composition is close to the ideal stoichiometry. The exchange vector of relevance for the studied system is ^M2(Mg,Fe²⁺) ^M4(Mg,Fe²⁺) ^M2Fe³⁺_–1 ^M4Li_–1, which is still rather unexplored in natural systems. Amphibole crystals of suitable size for structure refinement were obtained only at 800 °C, 0.4 GPa and NNO conditions (sample 152), and have C2/m symmetry. The X-ray powder patterns for all other samples were indexed in the same symmetry; the amphibole closest to ideal composition has a = 9.428(1) Å, b = 17.878(3) Å, c = 5.282(1) Å, = 102.06(2)°, V = 870.8(3) ų. Mössbauer spectra show that Fe³⁺ is strongly ordered at M2 in all samples, whereas Fe²⁺ is disordered over the B and C sites. FTIR analysis shows that the amount of ^CFe²⁺ increases for increasingly reducing conditions. FTIR data also provide strong evidence for slight but significant amounts of Li at the A sites.     

P–V–T equation of state of Ca3Al2Si3O12 grossular garnet

The thermoelastic parameters of synthetic Ca₃Al₂Si₃O₁₂ grossular garnet were examined in situ at high-pressure and high-temperature by energy dispersive X-ray diffraction, using a Kawai-type multi-anvil press apparatus coupled with synchrotron radiation. Measurements have been conducted at pressures up to 20 GPa and temperatures up to 1,650 K: this P, T range covered the entire high-P, T stability field of grossular garnet. The analysis of room temperature data yielded V _0,300 = 1,664 ± 2 ?³ and K ₀ = 166 ± 3 GPa for K^￠₀ K^{\prime}_{0} fixed to 4.0. Fitting of our P–V–T data by means of the high-temperature third order Birch–Murnaghan or the Mie–Grüneisen–Debye thermal equations of state, gives the thermoelastic parameters: (∂K _0,T /∂T) _P  = −0.019 ± 0.001 GPa K⁻¹ and α _0,T  = 2.62 ± 0.23 × 10⁻⁵ K⁻¹, or γ ₀ = 1.21 for fixed values q ₀ = 1.0 and θ ₀ = 823 (Isaak et al. Phys Chem Min19:106–120, 1992). From the comparison of fits from two different approaches, we propose to constrain the bulk modulus of grossular garnet and its pressure derivative to K _T0 = 166 GPa and K^￠_T0 K^{\prime}_{T0}  = 4.03–4.35. Present results are compared with previously determined thermoelastic properties of grossular-rich garnets.     

Thermodynamic analysis of the system Na2O-K2O-CaO-Al2O3-SiO2-H2O-F2O?1: Stability of fluorine-bearing minerals in felsic igneous suites

Thermodynamic analysis of the system Na₂O-K₂O-CaO-Al₂O₃-SiO₂-H₂O-F₂O_–1 provides phase equilibria and solidus compatibilities of rock-forming silicates and fluorides in evolved granitic systems and associated hydrothermal processes. The interaction of fluorine with aluminosilicate melts and solids corresponds to progressive fluorination of their constituent oxides by the thermodynamic component F₂O_–1. The chemical potential (F₂O_–1) buffered by reaction of the type: MO_n/2 (s)+n/2 [F₂O_–1]=MF_n (s, g) where M=K, Na, Ca, Al, Si, explains the sequential formation of fluorides: carobbiite, villiaumite, fluorite, AlF₃, SiF₄ as well as the common coexistence of alkali- and alkali-earth fluorides with rock-forming aluminosilicates. Formation of fluorine-bearing minerals first starts in peralkaline silica-undersaturated, proceeds in peraluminous silica-oversaturated compositions and causes progressive destabilization of nepheline, albite and quartz, in favour of villiaumite, cryolite, topaz, chiolite. Additionally, it implies the increase of buffered fluorine solubilities in silicate melts or aqueous fluids from peralkaline silica-undersaturated to peraluminous silica-oversaturated environments. Subsolidus equilibria reveal several incompatibilities: (i) topaz is unstable with nepheline or villiaumite; (ii) chiolite is not compatible with albite because it only occurs only at very high F₂O_–1 levels. The stability of topaz, fluorite, cryolite and villiaumite in natural felsic systems is related to their peralkalinity (peraluminosity), calcia and silica activity, and linked by corresponding chemical potentials to rock-forming mineral buffers. Villiaumite is stable in strongly peralkaline and Ca-poor compositions (An_<0.001). Similarly, cryolite stability requires coexistence with nearly-pure albite (An_<2). Granitic rocks with Ca-bearing plagioclase (An_>5) saturate with topaz or fluorite. Crystallization of topaz is restricted to peraluminous conditions, consistent with the presence of Li-micas or anhydrous aluminosilicates (cordierite, garnet, andalusite). Fluorite is predicted to be stable in peraluminous biotite granites, amphibole-, clinopyroxene- or titanite-bearing calc-alkaline suites as well as in peralkaline granitic and syenitic rocks. Fluorine concentrations in felsic melts buffered by the coexistence of F-bearing minerals and feldspars increase from peralkaline through metaluminous to mildly peraluminous compositions. At low-temperature conditions, the hydrothermal evolution of peraluminous granitic and greisen systems is controlled by white mica-feldspar-fluoride equilibria. With decreasing temperature, topaz gradually breaks down via: (i) (OH)F_–1 substitution and fluorine transfer to fluorite by decalcification of plagioclase below 600 °C, (ii) formation of muscovite and additional fluorite at 475–315 °C, and (iii) formation of paragonite and cryolite, consuming F-rich topaz and albite below 315 °C. These equilibria explain the absence of magmatic fluorite in Ca-bearing topaz granitic rocks; its abundance in hydrothermal rocks is due to: (i) closed-system defluorination of topaz, (ii) open-system decalcification of plagioclase or (iii) hydrolytic alteration. These results provide a complete framework for the investigation of fluorine-bearing mineral stabilities in felsic igneous suites.Electronic Supplementary Material Supplementary material is available in the online version of this article at . A link in the frame on the left on that page takes you directly to the supplementary material.Editorial responsibility: T.L. Grove     

Synchrotron X-ray analysis of norbergite, Mg2.98Fe0.01Ti0.02Si0.99O4(OH0.31F1.69) structure at high pressure up to 8.2?GPa

The natural norbergite, Mg_2.98Fe_0.01Ti_0.02Si_0.99O₄(OH_0.31F_1.69) is examined by synchrotron X-ray diffraction analysis at pressures up to 8.2 GPa. The measured linear compressibilities of the crystallographic axes are β _a  = 2.18(4) × 10⁻³, β _b  = 2.93(7) × 10⁻³, and β _c  = 2.77(7) × 10⁻³ (GPa⁻¹), respectively and the calculated isothermal bulk modulus of the norbergite is K _T = 113(2) GPa based on the Birch–Murnaghan equation of state assuming a pressure derivative of K′ = 4. The crystal structures of norbergite are refined at room temperature and pressures of 4.7, 6.3, and 8.2 GPa, yielding R values for the structure refinements of 4.6, 5.3, and 5.3%, respectively. The bulk moduli of the polyhedral sites are 293(15) GPa for the tetrahedron, 106(5) GPa for the M2 octahedron, 113(2) GPa for the M3 octahedron, and 113(3) GPa for the total void space. The bulk modulus exhibits a good linear correlation with the filling factor for polyhedral sites in structures of the humite minerals and forsterite, reflecting the Si⁴⁺ + 4O²⁻ ⇔ □ + 4(OH, F)⁻ substitution in the humite minerals. Moreover, two simply linear trends were observed in the relationship between bulk modulus and packing index for natural minerals and dense hydrous magnesium silicate minerals. This relationship would reflect that the differences in compression mechanism were involved with hydrogen bonding in these minerals. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Burovaite-Ca, (Na,K)4Ca2(Ti,Nb)8[Si4O12]4(OH,O)8·12H2O, a new labuntsovite-group mineral species and its place in low-temperature mineral formation in pegmatites of the Khibiny pluton, Kola Peninsula, Russia

This paper presents data on burovaite-Ca, the first Ti-dominant member of the labuntsovite group with a calcium D-octahedron. The idealized formula of burovaite-Ca is (K,Na)₄Ca₂(Ti,Nb)₈[Si₄O₁₂]₄(OH,O)₈ · 12H₂O. The mineral has been found in the hydrothermal zone of aegirine-microcline pegmatite located in khibinite at Mt. Khibinpakhkchorr, the Khibiny pluton, Kola Peninsula, Russia. Radiaxial intergrowths of burovaite-Ca and labuntsovite-Mn associated with lemmleynite-Ba, analcime, and apophyllite have been identified in caverns within microcline. The mean composition of the mineral is as follows, wt %: 3.72 Na₂O, 2.76 K₂O, 4.22 CaO, 0.47 SrO, 0.23 BaO, 0.01 MnO, 0.30 Fe₂O₃, 0.14 Al₂O₃, 42.02 SiO₂, 17.30 TiO₂, 15.21 Nb₂O₅, 12.60 H₂O (measured); the total is 98.98. Its empirical formula has been calculated on the basis of [(Si,Al)₁₆O₄₈]: {(Na_3.10K_1.07Ca_0.37Sr_0.04Ba_0.04)_4.62}(Ca_1.28Zn_0.01)_1.29(Ti_4.97Nb_2.56Fe_0.08Ta_0.02)_7.63(Si_15.93Al_0.07)₁₆O₄₈(OH_6.70O_0.93)_7.63 · 12H₂O. The strongest lines in the X-ray powder diffraction pattern of burovaite-Ca (I-d ?] are as follows: 70–7.08, 40–6.39, 40–4.97, 30–3.92, 40–3.57, 100–3.25, 70–3.11, 50–2.61, 70–2.49, 40–2.15, 50–2.05, 70–1.712, 70–1.577, and 70–1.444. The structure of burovaite-Ca was solved by A.A. Zolotarev, Jr. The mineral is monoclinic, space group C2/m. The unit-cell dimensions are a = 14.529(3), b = 14.203(3), c = 7.899(1), β = 117.37(1)°, V = 1447.57 ?₃. Burovaite-Ca is an isostructural Ti-dominant analogue of karupm?llerite-Ca and gjerdingenite-Ca. Two stages of mineral formation—pegmatite proper and hydrothermal—have been recognized in the host pegmatite. The hydrothermal stage included K-Ba-Na, Na-K-Ca, and Na-Sr substages. Burovaite-Ca is related to the intermediate Na-K-Ca substage. At the first substage, labuntsovite-Mn and lemmleynite-Ba were formed, and tsepinite-Na, paratsepinite-Nd, and tsepinite-Sr were formed at the final substage. Thus, the sequence of crystallization of labuntsovite-group minerals is characterized by the replacement of the potassium regime by the sodium regime of alkaline solutions in the evolved host pegmatite.     

Schüllerite, Ba2Na(Mn,Ca)(Fe3+,Mg,Fe2+)2Ti2(Si2O7)2(O,F)4, a new mineral species from the Eifel volcanic district, Germany

A new heterophyllosilicate mineral schüllerite was found in the L?hley basalt quarry in the Eifel volcanic region, Germany, as a member of the late mineral assemblage comprising nepheline, leucite, augite, phlogopite, magnetite, titanite, fresnoite, barytolamprophyllite, fluorapatite, perovskite, and pyrochlore. Flattened brown crystals of schüllerite up to 0.5 × 1 × 2 mm in size and their aggregates occur in miarolic cavities of alkali basalt. The mineral is brittle, with a Mohs hardness 3–4 and perfect cleavage parallel to (001). D _calc = 3.974 g/cm³. Its IR spectrum is individual and does not contain bands of OH⁻, CO₃²⁻ or H₂O. Schüllerite is biaxial (−), α = 1.756(3), β = 1.773(4), γ = 1.780(4), 2V _meas = 40(20)°. Dispersion is weak, r < ν. Pleochroism is medium X > Y > Z, brown to dark brown. Chemical composition (electron microprobe, mean of five-point analyses, Fe²⁺/Fe³⁺ ratio determined by the X-ray emission spectroscopic data, wt %): 3.55 Na₂O, 0.55 K₂O, 3.89 MgO, 2.62 CaO, 1.99 ArO, 28.09 BaO, 3.43 FeO, 8.89 Fe₂O₃, 1.33 Al₂O₃, 11.17 TiO₂, 2.45 Nb₂O₅, 26.12 SiO₂, 2.12 F, −0.89 -O=F₂, 98.98 in total. The empirical formula is (Ba_1.68Sr_0.18K_0.11Na_1.05Ca_0.43Mn_0.47Mg_0.88Fe_0.44²⁺Fe_1.02³⁺Ti_1.28Nb_0.17Al_0.24)_Σ7.95Si_3.98O_16.98F_1.02. The crystal structure was refined on a single crystal. Schüllerite is triclinic, space group P1, unit cell parameters: a = 5.4027(1), b = 7.066(4), c = 10.2178(1)?, α = 99.816(1), β = 99.624(1), γ = 90.084(1)°, V = 378.75(2) ?³, Z = 1. The strongest lines of the X-ray powder diffraction pattern [d, ?, (I, %)]: 9.96(29), 3.308(45), 3.203(29), 2.867(29), 2.791(100), 2.664(46), 2.609(36), 2.144(52). The mineral was named in honor of Willi Schüller (born 1953), an enthusiastic, prominent amateur mineral collector, and a specialist in the mineralogy of Eifel. Type specimens have been deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, registration no. 3995/1,2.     

Influence of oxygen fugacity on the solubility of nitrogen, carbon, and hydrogen in FeO-Na2O-SiO2-Al2O3 melts in equilibrium with metallic iron at 1.5 GPa and 1400°C

It is assumed in the theories of Earth formation that the composition of gases extracted by primary planetary magmas is formed by the large-scale melting of the early mantle, which occurred in the presence of a metallic Fe phase. The molten Fe metal and silicate materials underwent gravitational migration, which affected the fractionation of siderophile elements. Volatile compounds had to form simultaneously in the zones of large-scale melting of the early Earth; their compositions were controlled by interaction with silicate and metallic melts. This process remains poorly understood.     

Nanoinclusions of high-pressure hydrous silicate, Mg3Si4O10(OH)2 · n H2O (10?-phase), in mantle olivine: Mechanisms of formation and transformation

The 10?-phase, Mg₃Si₄O₁₀(OH)₂ · nH₂O, where n = 0.65÷2, belongs to the group of dense hydrous magnesium silicates (DHMS), which were produced in experiments and are regarded as hypothetical mineral carriers for H₂O in the mantle. However, DHMS were almost never observed in nature. The only exception is the finding of the 10?-phase as nanoinclusions in olivines from mantle nodules in kimberlites. The inclusions with sizes of a few ten nanometers have a pseudohexagonal habit and are characterized by the presence of voids free of solids. The 10?-phase fills the equatorial parts of the inclusions, and, in the majority of inclusions, it is replaced by the low-pressure serpentine + talc assemblage. Based on the analysis of electron microscope images, a model was proposed for the solid-state formation of inclusions, the precursory material of which was transformed to the 10?-phase with the liberation of a water fluid. According to this model, the formation of hydrous nanoinclusions and their subsequent autoserpentinization occurred without the influx of H₂O from the external medium through the mobilization of intrinsic hydroxyl-bearing point defects trapped during olivine crystallization. The subsequent autoserpentinization of the inclusions occurred during decompression owing to interaction between the inclusion material and the host olivine matrix. The process was accompanied by the partial exhaustion of the fluid phase and the replacement 10?-phase + H₂O = Serp + Tc. The criterion for the credibility of the model is the conservation of the volume of material during the reaction at P = const and T = const. Original Russian Text ? N.R. Khisina, R. Wirth, 2008, published in Geokhimiya, 2008, No. 4, pp. 355–363.     

交互四元体系Li+, Mg2+//SO2-4, B4O2-7H2O 288 K

采用等温溶解平衡法研究了288K时Li+, Mg2+//SO2-4, B4O2-7- H2O四元体系的固液相平衡关系,测定了该四元体系在288K时平衡液相的溶解度和密度。依据实验测定的平衡溶解度数据及对应的平衡固相,绘制了该四元体系的平衡相图及密度组成图。研究结果表明：交互四元体系Li+, Mg2+//SO2-4, B4O2-7- H2O 288K时平衡相图中有2个共饱点,5条单变量曲线,4个结晶区对应的平衡固相分别为Li2B4O7·3H2O,Li2SO4·H2O,MgB4O7·9H2O和MgSO4·7H2O。     

Eurekadumpite, (Cu,Zn)16(TeO3)2(AsO4)3Cl(OH)18·7H2O, a new supergene mineral species

A new mineral eurekadumpite found at the Centennial Eureka Mine in the Tintic district of Juab County in Utah in the United States occurs in the oxidation zone along with quartz, macalpineite, malachite, Zn-bearing olivenite, goethite, and Mn oxides. Eurekadumpite forms spherulites or rosettes up to 1 mm in size and their clusters and crusts up to 1.5 cm² in cavities. Its individuals are divergent and extremely thin (up to 0.5 mm across and less than 1 μm thick) hexagonal or roundish leaflets. The mineral is deep blue-green or turquoise-colored. Its streaks are light turquoise-colored. Its luster is satiny in aggregates and pearly on individual flakes. Its cleavage is (010) perfect and micalike. Its flakes are flexible but inelastic. Its Mohs hardness is 2.5–3.0, and D(meas) = 3.76(2) and D(calc) = 3.826 g/cm³. The mineral is optically biaxial negative, and α = 1.69(1), β ∼ γ = 1.775(5), and 2V _meas = 10(5)°. Its pleochroism is strong: Y = Z = deep blue-green, and X = light turquoise-colored. Its orientation is X = b. The wavenumbers of the bands in the IR spectrum (cm⁻¹; the strong lines are underlined, and w denotes the weak bands) are 3400, 2990, 1980w, 1628, 1373w, 1077, 1010, 860, 825, 803, 721w, 668, 622, 528, 461. The IR spectrum shows the occurrence of the tellurite (Te⁴⁺,O₃)²⁻ and arsenate (As⁵⁺,O₄)³⁻ anionic groups and H₂O molecules; Cu and Zn cations are combined with OH⁻ groups. The chemical composition of eurekadumpite is as follows (wt %, average of 14 electron-microprobe analyses; H₂O determined using the Alimarin method): 0.04 FeO, 36.07 CuO, 20.92 ZnO, 14.02 TeO₂, 14.97 As₂O₅, 1.45 Cl, 13.1 H₂O, O = Cl₂ −0.33, total 100.24. The empirical formula based on 2 Te atoms is (Cu_10.32Zn_5.85Fe_0.01)_Σ16.18(TeO₃)₂(AsO₄)_2.97[Cl_0.93(OH)_0.07]_Σ1(OH)_18.45 · 7.29H₂O. The idealized formula is (Cu,Zn)₁₆(TeO₃)₂(AsO₄)₃Cl(OH)₁₈ · 7H₂O. Eurekadumpite is monoclinic (pseudohexagonal), and the most probable space groups are P2/m, P2, or Pm. The unit-cell parameters refined from the powder X-ray data are as follows: a = 8.28(3), b = 18.97(2), c = 7.38(2) ?, β = 121.3(6)°, V = 990(6) ?³, and Z = 1. The strongest reflections of the X-ray powder pattern (d, ? (I) [hkl]) are as follows: 18.92(100) [010], 9.45(19) [020], 4.111(13) [[`2]\bar 2 01], 3.777(24) [050, [`2]\bar 2 21, 041], 2.692(15) [[`3]\bar 3 11, 151, [`3]\bar 3 02], 2.524(41)[170, [`2]\bar 2 52, [`1]\bar 1 71], 1.558(22) [[`4]\bar 4 82, [`3]\bar 3 .10.1, 024]. The name of the mineral means, firstly, that it was found in specimens from dumps of the Centennial Eureka Mine. In addition, it could mean found in a dump (the Greek word eureka means I have found it). There is an allusion to the great role that dumps of abandoned mines have played in the discovery of new minerals. Type specimens are deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences in Moscow, at the Smithsonian National Museum of Natural History in Washington, and at the American Museum of Natural History in New York.     

A multi-isotope (δD, δO,Sr/Sr,and δB) approach for identifying saltwater intrusion and resolving groundwater evolution along the Western Caprock Escarpment of the Southern High Plains,New Mexico

Declining water levels in arid and semi-arid regions increase an aquifer’s vulnerability to natural and anthropogenic influences. A multi-isotope (δD, δ¹⁸O, ⁸⁷Sr/⁸⁶Sr, and δ¹¹B) approach was used to resolve the geochemical evolution of groundwater in a declining aquifer in a semi-arid region of the southwestern USA as groundwater composition reacts to source-water mixing, cross-formational flow including saltwater intrusion, water–rock interaction, and likely agricultural recharge. Sub-aquifers or local flow systems are present in the Southern High Plains aquifer along the Western Caprock Escarpment in New Mexico, and the study site’s local flow system contains a Na–Cl, high dissolved-solids groundwater that flows from the escarpment until it mixes with a high quality regional aquifer or regional flow system. The local flow system contains water that is similar in composition to the underlying, upper Dockum Group aquifer. Saltwater found in the upper Dockum Group aquifer likely originates in the adjacent Pecos River Basin and crosses beneath or possibly through the hydrologic divide of the Western Caprock Escarpment. Strontium concentrations of 0.9–31 mg/L and a ⁸⁷Sr/⁸⁶Sr range of 0.70845–0.70906 were sufficient to estimate source-water fractions, mixing patterns, and contributions from chemical weathering through mass balance inverse calculations. Boron concentrations (59–1740 mg/L) and δ¹¹B values (+6.0–+46.0‰) were used to confirm source-water mixing, further evaluate water–rock interaction, and examine the influence of possible agricultural recharge. Alteration of B concentrations and δ¹¹B values in an area of likely agricultural recharge indicated the loss of B and decrease in δ¹¹B values likely from plant uptake, adsorption, and weathering contributions in the soil/vadose zone prior to recharge. The effectiveness of ⁸⁷Sr/⁸⁶Sr and δ¹¹B for resolving the geochemical influences in groundwater in the Southern High Plains along the Western Caprock Escarpment allowed for the reinterpretation of the isotopic composition of water that has been shown to be highly variable in the Southern High Plains. This study shows the utility of a multi-isotope approach for resolving the geochemical evolution of groundwater in an aquifer that has a complex relationship with underlying aquifers and the applicability of these isotopes as indicators of the alteration of source waters from natural or anthropogenic influences.     

Shlykovite KCa[Si4O9(OH)] · 3H2O and cryptophyllite K2Ca[Si4O10] · 5H2O, new mineral species from the Khibiny alkaline pluton, Kola Peninsula, Russia

New minerals, shlykovite and cryptophyllite, hydrous Ca and K phyllosilicates, have been identified in hyperalkaline pegmatite at Mount Rasvumchorr, Khibiny alkaline pluton, Kola Peninsula, Russia. They are the products of low-temperature hydrothermal activity and are associated with aegirine, potassium feldspar, nepheline, lamprophyllite, eudialyte, lomonosovite, lovozerite, tisinalite, shcherbakovite, shafranovskite, ershovite, and megacyclite. Shlykovite occurs as lamellae up to 0.02 × 0.02 × 0.5 mm in size or fibers up to 0.5 mm in length usually combined in aggregates up to 3 mm in size, crusts, and parallel-columnar veinlets. Cryptophyllite occurs as lamellae up to 0.02 × 0.1 × 0.2 mm in size intergrown with shlykovite being oriented parallel to {001} or chaotically arranged. Separate crystals of the new minerals are transparent and colorless; the aggregates are beige, brownish, light cream, and pale yellowish-grayish. The cleavage is parallel to (001) perfect. The Mohs hardness of shlykovite is 2.5–3. The calculated densities of shlykovite and cryptophyllite are 2.444 and 2.185 g/cm³, respectively. Both minerals are biaxial; shlykovite: 2V _meas = −60(20)°; cryptophyllite: 2V _meas > 70°. The refractive indices are: shlykovite: α = 1.500(3), β = 1.509(2), γ = 1.515(2); cryptophyllite: α = 1.520(2), β = 1.523(2), γ = 1.527(2). The chemical composition of shlykovite determined by an electron microprobe (H₂O determined from total deficiency) is as follows, wt %: 0.68 Na₂O, 11.03 K₂O, 13.70 CaO, 59.86 SiO₂, 14.73 H₂O; the total is 100.00. The empirical formula calculated on the basis of 13 O atoms (OH/H₂O calculated from the charge balance) is (K_0.96Na_0.09)_Σ1.05Ca_1.00Si_4.07O_9.32(OH)_0.68 · 3H₂O. The idealized formula is KCa[Si₄O₉(OH)] · 3H₂O. The chemical composition of cryptophyllite determined by an electron microprobe (H₂O determined from the total deficiency) is as follows, wt %: 1.12 Na₂O, 17.73 K₂O, 11.59 CaO, 0.08 Al₂O₃, 50.24 SiO₂, 19.24 H₂O, the total is 100.00. The empirical formula calculated on the basis of (Si,Al)₄(O,OH)₁₀ (OH/H₂O calculated from the charge balance) is (K_1.80Na_0.17)_Σ1.97Ca_0.99Al_0.01Si_3.99O_9.94(OH)_0.06 · 5.07H₂O. The idealized formula is K₂Ca[Si₄O₁₀] · 5H₂O. The crystal structures of both minerals were solved on single crystals using synchrotron radiation. Shlykovite is monoclinic; the space group is P2₁/n; a = 6.4897(4), b = 6.9969(5), c = 26.714(2)?, β = 94.597(8)°, V = 1209.12(15)?³, Z = 4. Cryptophyllite is monoclinic; the space group is P2₁/n; a = 6.4934(14), b = 6.9919(5), c = 32.087(3)?, β = 94.680(12)°, V= 1451.9(4)?, Z = 4. The strongest lines of the X-ray powder patterns (d, ?-I, [hkl] are: shlykovite 13.33–100[002], 6.67–76[004], 6.47–55[100], 3.469–45[021], 3.068–57[$ \bar 1 $ \bar 1 21], 3.042–45[121], 2.945–62[ 23], 2.912–90[025, 12, 211]; cryptophyllite 16.01–100[002], 7.98–24[004], 6.24–48[101], 3.228–22[$ \bar 1 $ \bar 1 09], 3.197–27[0.0.10], 2.995–47[122], 2.903–84[123, 204, $ \bar 1 $ \bar 1 24, 211], 2.623–20[028, 08, 126]. Shlykovite and cryptophyllite are members of new related structural types. Their structures are based on a two-layer packet consisting of tetrahedral Si layers linked with octahedral Ca chains. Mountainite, shlykovite and cryptophyllite could be combined into the mountainite structural family. Shlykovite is named in memory of Russian geologist V. G. Shlykov (1941–2007); the name cryptophyllite is from the Greek words meaning concealed and leaf that allude to its layered structure (phyllosilicate) in combination with a lamellar habit and intimate intergrowths with visually indistinguishable shlykovite. Type specimens of the minerals are deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow.     

纤钡锂石 BaMg2LiAl3[Si2O6]2（OH,F）8及其晶体结构

1974年在一水晶矿石英脉晶洞中,发现了一种含Ba、Li的硅酸盐新矿物--纤钡锂石。我们对纤钡锂石进行了光性研究、比重测定、差热及热失重分析、红外光谱分析、X射线单晶结构分析等工作,现分述如下。     

Thermal behavior of ferric selenite hydrates (Fe2(SeO3)3·3H2O,Fe2(SeO3)3·5H2O) and the water content in the natural ferric selenite mandarinoite

Any progress in our understanding of low-temperature mineral assemblages and of quantitative physico-chemical modeling of stability conditions of mineral phases, especially those containing toxic elements like selenium, strongly depends on the knowledge of structural and thermodynamic properties of coexisting mineral phases. Interrelation of crystal chemistry/structure and thermodynamic properties of selenium-containing minerals is not systematically studied so far and thus any essential generalization might be difficult, inaccurate or even impossible and erroneous. Disagreement even exists regarding the crystal chemistry of some natural and synthetic selenium-containing phases. Hence, a systematic study was performed by synthesizing ferric selenite hydrates and subsequent thermal analysis to examine the thermal stability of synthetic analogues of the natural hydrous ferric selenite mandarinoite and its dehydration and dissociation to unravel controversial issues regarding the crystal chemistry. Dehydration of synthesized analogues of mandarinoite starts at 56–87?°C and ends at 226–237?°C. The dehydration happens in two stages and two possible schemes of dehydration exist: (a) mandarinoite loses three molecules of water in the first stage of the dehydration (up to 180?°C) and the remaining two molecules of water will be lost in the second stage (>180?°C) or (b) four molecules of water will be lost in the first stage up to 180?°C and the last molecule of water will be lost at a temperature above 180?°C. Based on XRD measurements and thermal analyses we were able to deduce Fe₂(SeO₃)₃·(6-x)H₂O (x?=?0.0–1.0) as formula of the hydrous ferric selenite mandarinoite. The total amount of water apparently affects the crystallinity, and possibly the stability of crystals: the less the x value, the higher crystallinity could be expected.     

三元体系K+,Mg2+∥B4O72--H2O 348K稳定相平衡研究

采用等温溶解平衡法开展了三元体系K+,Mg2+∥B4O72--H2O 348K的稳定相平衡研究,获得溶解度数据及平衡液相的密度,折光率,pH值。根据溶解度数据绘制了三元体系稳定相图。该三元体系在348K时的稳定相图含有一个共饱点E、两条单变量曲线AE,BE和两个结晶相区MgB4O7.9H2O(AECA)和K2B4O7·4H2O(BEDB)。共饱点的平衡固相组成为MgB4O7·9H2O和K2B4O7·4H2O,对应的平衡液相组成为w(K2B4O7)=42.28%、w(MgB4O7)=8.11%。研究结果表明,该三元体系属于简单共饱和型,无复盐和固溶体形成。K2B4O7·4H2O和MgB4O7·9H2O互相存在盐溶作用,使得这两种盐的溶解度明显增大。平衡液相的密度、折光率均随溶液中K2B4O7质量分数的增大而增大。     

大气气溶胶中NO3- ,SO42-研究

根据对国内外有关文献资料的总结归纳，对气溶胶中ＮＯ＾－３，ＳＯ＾２－４的研究现状及其在不同类型样品中的浓度量值分别进行了阐述；对雪冰层中的ＮＯ＾－３和ＳＯ＾２－４进行了本底划分，并对这些本底的来源，组成及特征进行了分析。