Two crystals of the uranyl carbonate mineral grimselite, ideally K3Na[(UO2)(CO3)3](H2O), from Jáchymov in the Czech Republic were studied by single-crystal X-ray diffraction and electron-probe microanalysis. One crystal has considerably more Na than the ideal chemical composition due to substitution of Na into KO8 polyhedra; the composition of the other crystal is nearer to ideal, and similar to synthetic grimselite. The presence of Na atoms in KO8 polyhedra, which are located in channels in the crystal structure, reduces their volume, and as a result the unit-cell volume also decreases. Structure refinement shows that the formula for the sample with the anomalously high Na content is (K2.43Na0.57)Σ3.00Na[(UO2)(CO3)3](H2O). The unit-cell parameters, refined in space group P2c, are a = 9.2507(1), c = 8.1788(1) Å, V = 606.14(3) Å3 and Z = 2. The crystal structure was refined to R1 = 0.0082 and wR1 = 0.0185 with a GOF = 1.33, based on 626 observed diffraction peaks [Iobs>3σ(I)].

The crystal structure of the rare skarn mineral trabzonite, Ca4[Si3O9(OH)]OH, from the type locality near Ikizdere, Turkey and from the Upper Chegem caldera, Northern Caucasus, Kabardino-Balkaria, Russia has been solved and refined using single-crystal X-ray data. This shows that the chemical formula should be modified from Ca4(Si3O10)˙2H2O, reported in the original trabzonite description, to an OH-bearing composition. The crystal structure, which contains Si3O10 trimers embedded in a framework of CaO6–8 polyhedra, has orthorhombic symmetry, space group Ama2, a = 20.6, b = 9.1, c = 10.3 Å. The orthorhombic A-centred cell is easily obtained by transformation from the original monoclinic cell of P21/m symmetry. The revised formula means that trabzonite and foshagite are polymorphs; foshagite has wollastonite-like silicate chains and in contrast to trabzonite it does not contain silanol groups. The structure and composition of killalaite from both localities was also studied. Single-crystal X-ray structure refinement of killalaite from the Northern Caucasus confirmed it to be non-stoichiometric with a composition between Ca6[Si2O6(OH)]2(OH)2 and Ca7[Si2O7]2(OH)2(Z = 2). Trabzonite, killalaite and dellaite form a series of modular structures which differ mainly in the degree of condensation of the SiO4 units.

Kazanskyite, Ba & TiNbNa3Ti(Si2O7)2O2(OH)2(H2O)4, is a Group-III TS-block mineral from the Kirovskii mine, Mount Kukisvumchorr, Khibiny alkaline massif, Kola Peninsula, Russia. The mineral occurs as flexible and commonly bent flakes 2–15 μm thick and up to 330 μm across. It is colourless to pale tan, with a white streak and a vitreous lustre. The mineral formed in a pegmatite as a result of hydrothermal activity. Associated minerals are natrolite, barytolamprophyllite, nechelyustovite, hydroxylapatite, belovite-(La), belovite-(Ce), gaidonnayite, nenadkevichite, epididymite, apophyllite-(KF) and sphalerite. Kazanskyite has perfect cleavage on {001}, splintery fracture and a Mohs hardness of 3. Its calculated density is 2.930 g cm–3. Kazanskyite is biaxial positive with α 1.695, β 1.703, γ 1.733 (λ590 nm), 2Vmeas = 64.8(7)°, 2Vcalc = 55.4°, with no discernible dispersion. It is not pleochroic. Kazanskyite is triclinic, space group P, a 5.4260(9), b 7.135(1), c 25.514(4) Å, α 90.172(4), β 90.916(4), γ 89.964(3)°, V 977.61(3) Å3. The strongest lines in the X-ray powder-diffraction pattern [d(Å)(I)(hkl)] are: 2.813(100)(12,1), 2.149(82)(22,20,207,220,22), 3.938(70)(13,112), 4.288(44)(11,10,110,11), 2.128(44)(22,2,14,221,14,221,23), 3.127(39)(16,115), 3.690(36)(14), 2.895(33)(13,121) and 2.955(32)(10,120,12). Chemical analysis by electron microprobe gave Nb2O59.70, TiO219.41, SiO228.21, Al2O30.13, FeO 0.28, MnO 4.65, BaO 12.50, SrO 3.41, CaO 0.89, K2O 1.12, Na2O 9.15, H2O 9.87, F 1.29, O = F –0.54, sum 100.07 wt.%; H2O was determined from structure refinement. The empirical formula is (Na2.55Mn0.31Ca0.11Fe2+0.03)Σ3(Ba0.70Sr0.28K0.21Ca0.03)Σ1.22(Ti2.09Nb0.63Mn0.26Al0.02)Σ3Si4.05O21.42H9.45F0.59, calculated on 22 (O + F) a.p.f.u., Z = 2. The structural formula of the form AP2MH2MO4(Si2O7)2XO4XPMXPA(H2O)n is (Ba0.56Sr0.22K0.15Ca0.03☐0.04)Σ1(☐0.74Ba0.14Sr0.06K0.06)Σ1(Ti0.98Al0.0 2)Σ1(Nb0.63Ti0.37)Σ1(Na2.55Mn0.31Ca0.11Fe2+0.03)Σ3(Ti0.74Mn0.26)Σ1(Si2O7)2O2(OH1.41F0.59)Σ2(H2O)(☐0.74H2O0.26)Σ1(H2O)2.74. Simplified and ideal formulae are as follows: Ba(☐,Ba)Ti(Nb,Ti)(Na,Mn)3(Ti,Mn)(Si2O7)2O2(OH,F)2(H2O)4 and Ba☐TiNbNa3Ti(Si2O7)2O2(OH)2(H2O)4. The Raman spectrum of the mineral contains the following bands: 3462 cm–1 (broad) and 3545 and 3628 cm–1 (sharp). The crystal structure was solved by direct methods and refined to an R1 index of 8.09%. The crystal structure of kazanskyite is a combination of a TS (titanium silicate) block and an I (intermediate) block. The TS block consists of HOH sheets (H is heteropolyhedral and O is octahedral). The TS block exhibits linkage and stereochemistry typical for Group-III (Ti = 3 a.p.f.u.) Ti-disilicate minerals. The TS block has two different H sheets where (Si2O7) groups link to [5]-coordinated Ti and [6]-coordinated Nb polyhedra, respectively. There are two peripheral sites, AP(1,2), occupied mainly by Ba (less Sr and K) at 96% and 26%. There are two I blocks: the I1 block is a layer of Ba atoms; the I2 block consists of H2O groups and AP(2) atoms. The TS and I blocks are topologically identical to those in the nechelyustovite structure. The mineral is named in honour of Professor Vadim Ivanovich Kazansky, a prominent Russian ore geologist and an expert in Precambrian metallogeny.

A detailed crystal-chemical study of the complex layered silicate molybdophyllite was conducted using single-crystal X-ray diffraction (XRD) methods, supplemented by powder XRD, infrared (IR) and Raman spectroscopic studies, chemical analyses by energy-dispersive spectrometry (EDS) on a scanning electron microscope (SEM), and electron probe microanalysis (EPMA). The results, based on several samples from both Långban and Harstigen, Filipstad, Sweden, show that the crystal structure of molybdophyllite has an order-disorder (OD) character. The latter is especially evident in specimens from Långban which display a complex diffraction pattern characterized by the simultaneous presence of sharp spots, diffuse reflections and continuous streaks. The sharp reflections define the unit cell of the family structure (a = 3.124, c = 41.832 Å, space group R32). Two main polytypes (maximum degree of order structures) are indicated by the OD approach: a trigonal one and a monoclinic one; the latter polytype is the most common in the samples that were studied and has space group C2, with a = 16.232(6), b = 9.373(2), c = 14.060(3) Å, b = 97.36(4)º and V = 2121.5(10) Å3.

The crystal structure determination [R1 = 0.096], together with the EPMA, IR and Raman data, reveal that molybdophyllite is built up by a regular alternation of complex layers with a composition {Mg9[Si10O28(OH)8][OPb4]2}6+ and simple layers with a composition [(CO3)3·H2O]6–, leading to the ideal crystal-chemical formula Pb8Mg9[Si10O28(OH)8|O2|(CO3)3]·H2O (Z = 2).

This contribution is mainly devoted to the results obtained for molybdophyllite sensu stricto, but new data for britvinite [i.e. 'molybdophyllite-18 Å'] are also presented and its modular relationship with molybdophyllite is discussed.

Matulaite was first described by Moore and Ito (1980) from the Bachman mine, Hellertown, Northampton County, Pennsylvania, USA. Its ideal formula was reported as CaAl18(PO4)12(OH)20·28H2O, based on wet-chemical analysis. Re-examination of both existing cotype specimens of matulaite revealed no material matching the powder or single-crystal X-ray diffraction data reported for the species. Other samples examined from the type locality, as well as from the LCA pegmatite in North Carolina, USA, and Fumade, Tarn, France, provided material crystallographically consistent with matulaite: P21/n, a = 10.604(2), b = 16.608(4), c = 20.647(5) Å , b = 98.848(7)° and Z = 4. Electron microprobe and crystal structure analysis of newly studied material from the type locality showed the ideal formula of matulaite to be Fe3+ Al7(PO4)4(PO3OH)2(OH)8(H2O)8˙8H2O. The chemical composition reported by Moore and Ito (1980) was most probably determined on a mixture of mostly kobokoboite and afmite, with lesser amounts of crandallite. As there is no matulaite on any of the existing cotype specimens of the species, the two specimens used to obtain the new chemical analyses, powder and single-crystal X-ray diffraction data and the structure determination are designated as neotypes. The neotypes have also been used to obtain crystal morphology and new measurements of the physical and optical properties of the species. The neotypes and new data have been approved by the CNMNC, proposal 11-F. The crystal structure of matulaite contains seven-member chain segments of AlO6 octahedra decorated by PO4 tetrahedra. The PO4 tetrahedra also link to isolated FeO6 octahedra, resulting in a 'pinwheel' Fe(PO4)6 group. The linkage of octahedra and tetrahedra defines a thick layer parallel to {001}. The only linkage between layers is via hydrogen bonding to interlayer water molecules.

Electron-microprobe analyses of Russian and Mongolian chevkinite-group minerals from little-known host lithologies, including various metasomatic rocks, quartzolites and an apatite deposit, are presented. The mineral species analysed include chevkinite-(Ce), perrierite-(Ce), polyakovite-(Ce) and Sr- and Zr-rich perrierite-(Ce). Compositional variation in the Sr-rich members of the group is broadly represented by the exchange vector (Fe + Mn + Al + REE) ↔ (Ca + Sr + Ti + Zr). Despite the varied parageneses, the chevkinite-(Ce) compositions are similar to previously published data. Many crystals have strong internal compositional variations, partly produced during primary crystallization and partly during low-temperature hydrothermal alteration.

The crystal structure and chemical composition of two samples of fettelite from the type locality, including a portion of the holotype material, was investigated to verify if a previously proposed revision of the chemical formula was applicable, and to study the role of cation substitution for Hg that would suggest new members of the fettelite family. The crystal structure of fettelite from the type locality was found to be equivalent to that reported previously for the Chilean occurrence, and consists of an alternation of two kinds of layers along c: layer A with general composition [Ag6As2S7]2– and layer B with general composition [Ag10HgAs2S8]2+. In this structure, the Ag atoms occur in various coordination configurations, varying from quasi-linear to quasi-tetrahedral, the AsS3 groups form pyramids as are typically observed in sulfosalts, and Hg links two sulfur atoms in a linear coordination. The refined compositions for the crystals in this study, [Ag6As2S7][Ag10(Fe0.53Hg0.47)As2S8] (R100124) and [Ag6As2S7][Ag10(Hg0.79Cu0.21)As2S8] (R110042), clearly indicate that new mineral species related to fettelite are likely to be found in nature.

Understanding the biogeochemical behaviour of actinides in the environment is essential for the longterm stewardship of radionuclide contaminated land. Plutonium is of particular concern due its high radiotoxicity, long half-life and complex chemistry, with these factors contributing to the limited literature available on its environmental behaviour. Here, we investigate the biogeochemistry of Pu in contaminated soil as microbial processes have the potential to mobilize Pu through numerous mechanisms including the reduction of Pu(IV) to the potentially more mobile Pu(III). After the addition of glucose to stimulate microbial activities, there was a substantial shift in the 16S rRNA gene profile of the extant microbial communities between days 0 and 44 with an increase in Clostridium species, known glucose fermenters which have been reported to facilitate the reduction of Pu(IV) to Pu(III). A minor increase in Pu mobility was observed at day 44, returning to initial levels by day 118. The negligible change in Pu mobility, despite the onset of reducing conditions and changing mineralogy, would suggest the Pu is highly refractory. This information is important for developing remediation options for Pu-contaminated soils, suggesting that managing legacy Pu in situ may be preferred to mobilization via the stimulation of metal-reducing bacteria.

Room temperature Mössbauer and electron-probe measurements of Fe3+/ΣFe in chromite from the mantle section of the Oman ophiolite define two groups of samples: a low Fe3+/ΣFe group (with Fe3+/ΣFe = 0.21–0.36) have cr# = Cr/(Cr + Al) in the range 0.49–0.75, whereas a smaller more geographically localized high Fe3+/ΣFe group (with Fe3+/ΣFe = 0.71–0.78) have a more restricted range of cr# ratios of 0.72–0.75. The low Fe3+/ΣFe chromitites have very variable Fe3+/ΣFe ratios. They are thought to have crystallized from melts that have interacted with depleted mantle and thereby acquired their variable Fe3+/ΣFe ratio. The high Fe3+/ΣFe chromitites are restricted to one small area of the mantle and their high oxidation state is thought to be post magmatic. They are either the product of later heating, related to melt flux or interaction with a later oxidising melt. A difference in oxygen fugacity between the MORB-depleted harzburgite host, which is at the quartz–fayalite–magnetite (QFM) buffer and the later chromite-bearing melts (QFM + 2) implies that there is a real difference in the oxidation state of the MORB and arc-magma sources.

Transparent prismatic crystals of Pb2(AsO2OH)Cl2 were collected in black metallurgical slag on the coast in the Punta Zeza area, 3 km south of the town of Lavrion, Greece. Analyses by energy-dispersive X-ray spectrometry (EDS) provided the following chemical composition: PbO 73.04, As2O3 15.97, Cl 11.42, O=Cl –2.58, total 97.85 wt.%. The empirical formula calculated on the basis of As = 1 is HxPb2.03(AsO3)1.00Cl1.995 (x = 0.96). The infrared spectrum of Pb2(AsO2OH)Cl2 has characteristic AsO33– bands at 707 and 594 cm–1, O–H stretching vibrations at 3310 and 2900 cm–1 and a band at 1107 cm–1 which is assigned to As–O–H bending vibrations. The structure, which is monoclinic P21/m, a = 6.4235(8), b = 5.5399(7), c = 9.321(1) Å, β = 90.767(2)°, V = 331.67(7) Å3, R1 = 0.035, is identical to that of synthetic Pb2(AsO2OH)Cl2 and contains two symmetrically unique Pb sites and one As site. The crystal structure is based on [Pb2AsO2OH]2+ double chains interconnected via weak Pb–Cl bonds to produce a three-dimensional framework which is closely related to that of Pb oxysalt minerals containing [O2Pb3]2+ chains of oxocentred [OPb4]6+ tetrahedra including mendipite, damaraite, rickturnerite and plumboselite.

Arsenohopeite, ideally Zn3(AsO4)2·4H2O, is the arsenate analogue of hopeite, Zn3(PO4)2·4H2O (it is isostructural with α-hopeite). It was found as a single colourless to blue crystalline grain from the Tsumeb mine, Namibia. The holotype specimen is ∼1 × 1 × 1 mm in size. Arsenohopeite is associated with tiny white fibres of an unidentified Zn- and As-bearing phase. It is orthorhombic, space group Pnma, with a = 10.804(2), b = 19.003(4), c = 5.112(1) Å, V = 1049.5(4) Å3 and Z = 4. Electron microprobe analysis yielded: ZnO 44.92, Fe2O3 0.92, MnO 0.51, MgO 0.20, CuO 0.02, As2O5 45.84 (wt.%). The empirical formula is (Zn2.80Fe0.06Mn0.04Mg0.03)Σ2.93(As1.01O4)2·4H2O, based on 12 oxygen atoms. Optically, the mineral is biaxial negative, with α = 1.598(2), β = 1.606(2), γ = 1.613(2) (white light) and 2Vcalc = 86°. It is not pleochroic or fluorescent. Arsenohopeite is translucent with a vitreous lustre. It is brittle, has an uneven fracture and (by analogy with hopeite) a cleavage that is perfect on {010}, good on {100} and poor on {001}. The calculated density is 3.420 g cm–3. The five strongest calculated powder diffraction lines are [d in Å (I)(hkl)]: 9.502 (100)(020), 2.926 (95)(241), 4.937 (50)(011), 4.110 (48)(230) and 3.567 (31)(240). The crystal structure of arsenohopeite has been solved by direct methods and refined in space group Pnma to R1 = 0.0353. Raman spectroscopy confirms the crystal-structure data and indicates the presence of weak hydrogen bonds.

The high-temperature (HT) behaviour of a sample of natural alunite was investigated by means of in situ HT single-crystal X-ray diffraction from room temperature up to the dehydroxylation temperature and consequent collapse of the crystal structure. In the temperature range 25–500°C, alunite expands anisotropically, with most of the contribution to volume dilatation being produced by expansion in the c direction. The thermal expansion coefficients determined over the temperature range investigated are: αa = 0.61(2) × 10–5 K–1 (R2 = 0.988), αc = 4.20(7) × 10–5 K–1 (R2 = 0.996), αc/αa = 6.89, αV = 5.45(7) × 10–5 K–1 (R2 = 0.998). At ∼275–300°C, a minor discontinuity in the variation of unit-cell parameters with temperature is observed and interpreted on the basis of loss of H3O+ that partially substitutes for K+ at the monovalent A site in the alunite structure. Increasing temperature causes the Al(O,OH)6 sheets, which remain almost unaltered along the basal plane, to move further apart, and this results in an expansion of the coordination polyhedron around the intercalated potassium cation. Sulfate tetrahedra act as nearly rigid units, they contract a little in the lower temperature range to accommodate the elongation of the Al octahedra.

Krásnoite is a new mineral (IMA2011-040) from the Huber open pit, Krásno ore district, Czech Republic and the Silver Coin mine, Nevada, USA. Krásnoite is the fluorophosphate analogue of perhamite. Krásnoite occurs as compact to finely crystalline aggregates, balls and rosette-like clusters up to 1 mm across. Individual crystals are platy, show a hexagonal outline and can reach 0.1 mm on edge at Krásno and 0.4 mm at Silver Coin. At both localities, krásnoite occurs very late in phosphaterich paragenetic sequences. Krásnoite crystals are partly transparent with a typically pearly lustre, but can also appear greasy (Krásno) or dull (Silver Coin). The streak is white and the hardness is 5 on the Mohs scale. Crystals are brittle, have an irregular fracture, one imperfect cleavage on {001} and are not fluorescent under SW and LW ultraviolet light. Penetration twinning ⊥ {001} is common. The density for both Krásno and Silver Coin material is 2.48(4) g cm–3, measured by the sink–float method in an aqueous solution of sodium polytungstate. The calculated density is 2.476 g cm–3 (Krásno). Krásnoite crystals are uniaxial (+), with ω = 1.548(2) and ε = 1.549(2) (Krásno) and ω = 1.541(1) and ε = 1.543(1) (Silver Coin). The simplified formula of krásnoite is: Ca3Al7.7Si3P4O23.5(OH)12.1F2·8H2O. Krásnoite is trigonal, space group Pm1, with a = 6.9956(4), c = 20.200(2) Å, V = 856.09(9) Å3 and Z = 3. Raman and infrared spectroscopy, coupled with magic-angle spinning nuclear magnetic resonance (MAS–NMR) spectrometry, confirmed the presence of PO3F, PO4, SiO4, H2O and OH in the crystal structure of krásnoite.

Strontium-rich epidote, including epidote-(Sr) and epidote with major amounts of Sr (i.e. epidote containing up to 17.3 wt.% SrO), was found in pumpellyite schist and epidote blueschist in a tectonic block in the serpentinite mélange of the Kurosegawa Zone, central Kyushu, Japan. The tectonic block is 20 m wide and made primarily of lawsonite blueschist, with subordinate amounts of pumpellyite schist and epidote blueschist. The pumpellyite schist typically occurs at the edge of the block and is composed mainly of pumpellyite with subordinate amounts of strontium-poor epidote, albite and chlorite, and thin veins of fine-grained calcite and clinopyroxene. Epidote-(Sr) forms rims around strontium-poor epidote, fills fractures in strontium-poor epidote and also occurs interstitially between pumpellyite aggregates and along the boundaries between pumpellyite and calcite-clinopyroxene veins. The epidote blueschist is found between the pumpellyite schist and lawsonite blueschist, and consists mainly of sodic amphibole, epidote and titanite, with albite veining. Strontium-rich epidote occurs as rims, replacing Sr-poor epidote near the albite vein. The bulk strontium contents of the rocks are as follows: lawsonite blueschist (200 ppm), epidote blueschist (2800 ppm) and pumpellyite schist (~10,700 ppm). The chemical and petrological characteristics of the Sr-rich epidote-bearing metabasites suggest that the infiltration of a metamorphic fluid promoted extensive Sr metasomatism during the later stages of high-pressure metamorphism.

A detailed electron microprobe (EMP) and laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) study of zircon from six types of miaskitic and agpaitic alkaline pegmatite from the Larvik Plutonic Complex, Oslo rift valley, Norway, was undertaken to shed light on the pegmatite petrogenesis. Detailed rare earth element (REE) analyses indicate important differences between the zircon from each type of pegmatite. Primary zircon from miaskitic Stavern-, Tvedalen- and Stålaker-type pegmatites has a mean ΣREE = 704 ppm, is depleted in LREE and has a significant positive Ce anomaly (Ce/Ce* = 44–67) and negative Eu anomaly (Eu/Eu* = 0.15–0.18). Secondary Tvedalen-type zircon is REE-enriched (ΣREE = 5035 ppm), with a flatter REE pattern, Ce/Ce* = 0.97 and a Eu anomaly similar to primary Tvedalen-type zircon (Eu/Eu* = 0.21). Secondary zircon from agpaitic Langesundsfjord-type pegmatites display a distinctive flat REE pattern characterized by overall REE enrichment (ΣREE = 967), Ce/Ce* = 1.92, and a minor negative Eu anomaly (Eu/Eu* = 0.37). Zircon from agpaitic Bratthagen-type pegmatites occurs as both altered primary and secondary phases and is strongly enriched in REE relative to other zircon (ΣREE = 4178 and 8388, respectively). Primary Bratthagen-type zircon has a similar REE pattern to miaskitic zircon, with a steeper HREE profile and smaller Ce and Eu anomalies (Eu/Eu* = 0.73; Ce/Ce* = 6.22). Secondary Bratthagen-type zircon is strongly enriched in LREE compared to primary zircon, does not display a positive Ce anomaly and has Eu/Eu* = 0.56. The altered primary and secondary Bratthagen-type zircons have elevated Th/UN ratios, suggesting a different melt source for Bratthagen-type agpaitic pegmatites. Zircon from external pegmatites has trace-element signatures similar to Stavern-, Tvedalen- and Staålaker-type primary zircon with Ce/Ce* = 214 and Nb/Ta and Th/U ratios that are similar to those of secondary Langesundsfjord- and Bratthagen-type zircon. It is suggested that the parental melt of the external pegmatites is the same as the miaskitic pegmatites, but that it has undergone alteration by hydrothermal fluids derived from the host basalt, or by post-magmatic F-rich fluids which mobilize Nb and Th. On the basis of texture, morphology and geochemistry, two populations of zircon can be recognized: (1) primary zircon from miaskitic pegmatites; and (2) secondary zircon from post-magmatic, hydrothermal assemblages. The U–Th–Pb isotope analyses indicate that the secondary and altered zircon are depleted in 238U, and enriched in LREE. Interaction of a post-magmatic hydrothermal fluid with an externally derived meteoric fluid is suggested to have influenced the REE signatures, and in particular the Eu and Ce anomalies of the late-stage zircons.

The new mineral calciolangbeinite, ideally K2Ca2(SO4)3, is the Ca-dominant analogue of langbeinite. It occurs in sublimates at the Yadovitaya fumarole on the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure eruption, Tolbachik volcano, Kamchatka, Russia. The mineral is associated with langbeinite, piypite, hematite, rutile, pseudobrookite, orthoclase, lyonsite, lammerite, cyanochroite and chlorothionite. Calciolangbeinite occurs as tetrahedral to pseudooctahedral crystals, which are bounded by {111} and {11}, and as anhedral grains up to 1 mm in size, aggregated into clusters up to 2 mm across, and forming crusts covering areas of up to 1.5x1.5 cm on the surface of volcanic scoria. Late-stage calciolangbeinite occurs in complex epitaxial intergrowths with langbeinite. Calciolangbeinite is transparent and colourless with white streak and vitreous lustre. Its Mohs' hardness is 3–3½. It is brittle, has a conchoidal fracture and no obvious cleavage. The measured and calculated densities are Dmeas = 2.68(2) and Dcalc = 2.74 g cm–3, respectively. Calciolangbeinite is optically isotropic with n = 1.527(2). The chemical composition of the holotype specimen is Na2O 0.38, K2O 21.85, MgO 6.52, CaO 16.00, MnO 0.27, FeO 0.08, Al2O3 0.09, SO3 55.14, total 100.63 wt.%. The empirical formula, calculated on the basis of twelve oxygen atoms per formula unit, is K2.01(Ca1.24Mg0.70Na0.05Mn0.02Fe0.01Al0.01)S 2.03S3.00O12. Calciolangbeinite is cubic, space group P213, a = 10.1887(4) Å, V = 1057.68(4) Å3 and Z = 4. The strongest reflections in the X-ray powder pattern [listed as (d, Å (I)(hkl)] are 5.84(8)(111); 4.54(9)(120); 4.15(27)(211); 3.218 (100) (310, 130); 2.838 (8) (230, 320), 2.736 (37) (231, 321), 2.006 (11) (431, 341) , 1.658(8)(611,532,352). The crystal structure was refined from single-crystal X-ray diffraction data to R = 0.0447. The structure is based on the langbeinite-type three-dimensional complex framework, which is made up of (Ca,Mg)O6 octahedra (Ca and Mg are disordered) and SO4 tetrahedra. Potassium atoms occupy two sites in voids in the framework; K(1) cations are located in ninefold polyhedra whereas K(2) cations are sited in significantly distorted octahedra. Calciolangbeinite and langbeinite are isostructural and form a solid-solution series.

Diamond and coesite occur in granulites of the Internal Zone of the Rif belt in northwest Africa. Diamond, identified by optical microscopy, electron microprobe analysis, Raman spectroscopy, cathodoluminescence and microstructural electron backscattered diffraction, is present as inclusions up to 20 μm across in garnet, K-feldspar, coesite relics and quartz. Thermobarometric estimates yield P >4.3 GPa and T >1100°C, which corresponds to a depth of formation >150 km. The estimates suggest that the diamond-bearing peridotites and adjacent crustal rocks experienced similar P–T conditions. If this is correct, there is an old (undated) core in the Betic–Rif cordillera and the current models of the tectonic evolution of the area, which are based on 'full Alpine' evolution, must be revised. This discovery provides further valuable information about the complex geotectonic environment of the southeast Spain and north Moroccan collisional orogen.

New electron-microprobe analyses of mayenite from the Ettringer Bellerberg volcano near Mayen in the Eifel district, Germany have high Cl contents and Raman spectroscopy indicates the presence of OH groups. Neither of these components is included in the generally accepted chemical formula, Ca12Al14O33. A refinement of the crystal structure by single-crystal X-ray methods reveals a previously unrecognized partial substitution. The O2 site which forms one of the apices of an AlO4 tetrahedron (with 3 × O1 sites) is replaced by 3 × O2a sites, which change the coordination of the central Al atom from tetrahedral to octahedral. This substitution is related to partial hydration of Ca12Al14O32Cl2 according to the isomorphic scheme (O2– + Cl–) ↔ 3(OH)–. The revised composition of Eifel mayenite is best described by the formula Ca12Al14O32–xCl2–x(OH)3x (x ∼0.75); the original formula, Ca12Al14O33, is inadequate. The analysed mineral can be considered to consist of endmember Ca12Al14O32Cl2 (62.5 mol.%) and endmember Ca12Al14O30(OH)6 (37.5 mol.%).

An article by A. C. Kerr and coworkers published in 2010 in Mineralogical Magazine (74, 1027–1036), reviewed an event that was interpreted as the eruption of a basaltic flow on 27th January 2010, at Tor Zawar, Ziarat, Pakistan. The regional and local geology, volcanological aspects, petrography and major-element and trace-element analyses of two samples were presented. On the basis of these data it was proposed that this was a magmatic event and that the lava was derived from the mantle. On the basis of our extensive field work in the this area, and observations at the site of another similar incident that happened almost a year later (in January 2011) ∼300 m north of the first locality, we wish to clarify the geological context and propose an alternative origin.

Our field observations suggest that both events were the result of localized surface melting at the base of metal electricity pylons, and their associated steel cable supports. The metal pylons and cable supports provided a path to earth for lightning discharges into the volcanic conglomerate of the Late Cretaceous Bibai Formation. We propose that this transmitted sufficient energy to melt the outcrop. We disagree with the proposal that the 'lava flows' at Tor Zawar were magmatic events and that the rocks formed are derived from the mantle. Alternatively, we propose that these 'lavas' were produced in a manner similar to fulgurites.

The composition, structure, X-ray powder diffraction pattern, optical properties, density, infrared, Raman and Mössbauer spectra, and thermal properties of a homogeneous sample of metavivianite from the Boa Vista pegmatite, near Galiléia, Minas Gerais, Brazil are reported for the first time. Metavivianite is biaxial (+) with α = 1.600(3), β = 1.640(3), γ = 1.685(3) and 2Vmeas = 85(5)°. The measured and calculated densities are Dmeas = 2.56(2) and Dcalc = 2.579 g cm–3. The chemical composition, based on electronmicroprobe analyses, Mössbauer spectroscopy (to determine the Fe2+:Fe3+ ratio) and gas chromatography (to determine H2O) is MgO 0.70, MnO 0.92, FeO 17.98, Fe2O3 26.60, P2O5 28.62, H2O 26.5; total 101.32 wt.%. The empirical formula is (Fe3+1.64Fe2+1.23Mg0.085Mn0.06)Σ3.015(PO4)1.98(OH)1.72·6.36H2O. Metavivianite is triclinic, P, a = 7.989(1), b = 9.321(2), c = 4.629(1) Å, α = 97.34(1), β = 95.96(1), γ = 108.59(2)°, V = 320.18(11) Å3 and Z = 1. The crystal structure was solved using a single-crystal techniques to an agreement index R = 6.0%. The dominant cations in the independent sites are Fe2+ and Fe3+, with multiplicities of 1 and 2, respectively. The simplified crystal-chemical formula for metavivianite is Fe2+ (Fe3+, Fe2+)2(PO4)2(OH,H2O)2·6H2O; the endmember formula is Fe2+Fe3+2(PO4)2(OH)2·6H2O, which is dimorphous with ferrostrunzite.