Calzirtite, essentially CaTiZr3O9, has been identified in residual soils from the Bukusu carbonatite complex in Uganda. A satisfactory ultrasonic technique was developed for cleaning the samples prior to studying their mineralogy. Other heavy minerals present include ilmenite, perovskite, melanite, apatite, zircon, and baddeleyite. The properties and composition of calzirtite are compared with the available data from occurrences in the U.S.S.R. The mineral has a metasomatic paragenesis and probably indicates the presence of carbonatized rocks at depth.

We are apt to regard selenite or transparent gypsum as a useless mineral, apart from the very small quantity used in plates for microscope work. It is the object of this paper to show that from the first, to at any rate the seventeenth century in Europe and to the first half of the nineteenth in South America, considerable use was made of it. For the classical period the argument is based upon the identification of lapis specularis as mainly, if not entirely, selenite. Most translators render the name as talc or mica, the first word probably a vulgar error for the second, while some admit gypsum to have been included; Bailey in his notes on Pliny considers that two passages suggest gypsum but gives the preference to mica, while Zeitler claims nearly all the passages referred to below for this mineral. Pliny is, of course, our chief authority: I give the relevant passages in Philemon Holland's translation as more in keeping with the greater part of this paper, adding notes and the original Latin where necessary.

The synthetic analogue of mineral stillwaterite, Pd8As3, was synthesised and its crystal structure was solved to R1 = 0.0341 based on single crystal X-ray diffraction data. Pd8As3 is trigonal and the space group is P$\bar{3}$. The unit-cell parameters are a = 7.4261(4), c = 10.3097(9) Å and V = 492.38(7) Å3 with Z = 3. The structure builds up by layers of Pd and As atoms. Pd-nets and As-nets are parallel to (110) and stack along the c axis direction. The stacking sequence is ABCDEEDCBA. The relation between structures of minerals with the common formula Pd8T3 (T = As or/and Sb) are discussed. They are formed by nets of pnictogen and palladium atoms. The common feature of the structures is 36 topology of pnictogen nets. The differences are stacking sequences and topology of the palladium nets.

A new occurrence of kintoreite, ideally PbFe3(PO4)(PO3OH)(OH)6, is described from the Tripi mine, Alì, Peloritani Mountains, northeastern Sicily, Italy. Kintoreite occurs as yellow equant crystals, up to 0.05 mm in size, on quartz, associated with another alunite-supergroup mineral currently under study. The studied grains of kintoreite are chemically zoned, showing the occurrence of two distinct domains. Electron microprobe analyses gave (in wt.%): SO3 5.47(27), P2O5 17.55(14), Al2O3 7.81(35), Fe2O3 23.81(44), PbO 35.11(41), H2Ocalc 9.93, total 99.68 (darker domains) and SO3 6.03(5), P2O5 16.66(23), Al2O3 4.22(2), Fe2O3 27.31(6), PbO 33.78(22), H2Ocalc 10.25, total 98.25 (brighter domains). On the basis of 14 O atoms per formula unit (apfu) and (P+S) = 2 apfu, the darker and brighter domains have chemical formula Pb1.00(Fe3+1.89Al0.97)Σ2.86[P1.57S0.43O7.43(OH)0.57][(OH)5.58(H2O)0.42]Σ6.00 and Pb0.98(Fe3+2.21Al0.53)Σ2.74[P1.51S0.49O7.49(OH)0.51][(OH)5.18(H2O)0.82]Σ6.00, respectively. Single-crystal X-ray diffraction was performed on a grain extracted from the same sample. Unit-cell parameters are a = 7.2191(10), c = 16.834(3) Å, V = 759.8(3) Å3 and Z = 3; space group R$\bar{3}$m. The crystal structure was refined on the basis of 226 unique reflections with Fo > 4σ(Fo) and 31 least-square parameters to R1 = 0.0415. Kintoreite is isotypic with other alunite-supergroup minerals. Micro-Raman spectroscopy suggests the possible occurrence of H2O groups, supporting the possible protonation of (OH) groups as a charge-balance mechanism in this mineral. Kintoreite may play an environmental role in the Alì area, where previous authors detected high concentrations of potentially toxic elements in soils.

Crimsonite (IMA2014-095), PbFe3+2(PO 4)2(OH)2, the phosphate analogue of carminite, is a new mineral from the Silver Coin mine, Valmy, Iron Point district, Humboldt County, Nevada, USA, where it occurs as a low-temperature secondary mineral in association with fluorwavellite, goethite, hematite, hentschelite, plumbogummite and variscite on quartz. Crimsonite occurs in subparallel aggregates of deep red blades or plates flattened on {100} and up to 0.1 mm in maximum dimension. The streak is light purplish orange. Crystals are transparent and have adamantine lustre. The Mohs hardness is ∼3½, the tenacity is brittle, the fracture is irregular to splintery and an imperfect cleavage is likely on {101}. The calculated density is 5.180 g/cm3. Crimsonite is optically biaxial (+), with 2V = 85.5(5)° and γ – α = 0.011. Using the Gladstone-Dale relationship, the calculated indices of refraction are α = 2.021, β = 2.026 and γ = 2.032. The optical orientation is X = b; Y = a; Z = c and the pleochroism is X light orange, Y light yellow, Z red brown; Y < X < Z. Electron microprobe analyses provided PbO 40.69, CaO 0.60, ZnO 0.72, CuO 0.13, Fe2O3 23.36, Al2O3 0.34, V2O5 0.70, As2O5 12.05, P2O5 16.03, SO3 0.33 and H2O 3.64 (structure), total 98.59 wt.%. The empirical formula (based on 10 O apfu) is (Pb1.06Ca0.06)∑1.12(Fe1.71Zn0.05Al0.04Cu0.01)∑1.81(P1.32As0.61V0.05S0.02)∑2.00O8[(OH)1.64(H2O)0.36]∑2.00. Crimsonite is orthorhombic, Cccm, a = 16.2535(13), b = 7.4724(4), c = 12.1533(9) Å, V = 1476.04(17) Å3 and Z = 8. The eight strongest lines in the powder X-ray diffraction pattern are [dobs in Å(I)(hkl)]: 5.86(42)(111); 4.53(45)(112); 3.485(64)(113); 3.190(100) (022); 3.026(40)(004); 2.902(54)(511); 2.502(77)(422) and 2.268(54)(224). The structure of crimsonite (R1 = 3.57% for 740 Fo > 4σF) contains FeO6 octahedra that share edges to form dimers, which are then linked to other dimers by corner sharing to form chains along [010]. These chains are linked by PO4 tetrahedra yielding sheets parallel to {001}. The sheets are linked to one another via bonds to 8-coordinated Pb2+ atoms with non-stereoactive 6s2 lone-electron pairs.

Tlapallite is a new mineral found in 1972 at the Bambollita (La Oriental) mine near Moctezuma, Sonora. Also recently found in old specimens from Tombstone, Arizona. Data for type (Mexican) material: Colour viridian green RHS-128A with pale streak, H = 3, D calc = 5·05 g/cm3. Crystals monoclinic, class unknown. Indexing based on Ito method gave a cell: a = 11·97 Å, b = 9·11, c = 15·66, β = 90 ° 36′. Strongest lines: 11·972 Å (10), 2·985 (10), 3·540 (6), 5·946 (5), 2·887 (5), 4·731 (4), 3·372 (4), 3·282 (4). Similar data obtain for Tombstone. Chemical analysis for type material yielded the formula H6Ca2Cu3(SO4)(TeO3)4,TeO6 with Te4+:Te6+ = 4:1. However, analysis of the Tombstone material indicates a more general formula H6(Ca, Pb)2(Cu, Zn)3(SO4) (TeO3)4,TeO6. The better data from this material indicate Z = 4, D calc = 5·465 vs D meas = 5·38. Characterized by extreme birefringence, α = 1·815, β = γ = 1·960; for Tombstone α = 1·955, β = γ = 2·115.

Named from the Nahua word tlapalli, meaning paint, in allusion to its mode of occurrence at the type locality.

The thermal expansions of trimerite and beryllonite have been determined up to 800°C. No anomalies were observed in the thermal expansion curves but the expansion coefficients for beryllonite are approximately twice those of trimerite. The thermal expansion behaviour of the minerals is interpreted in terms of a tetrahedral tilting model with the main change in apparent tilting being about the monoclinic 010 plane, i.e. the 0001 pseudo-hexagonal plane.

The analysis of an acid-soluble and acid-insoluble fraction of one systematically sampled, partially dolomitized limestone bed is reported. The original lime sediment, composed principally of skeletal remains, pellets, occasional intraclasts, detrital quartz, illite, and muscovite has been modified by the addition of calcite, dolomite, and dickite cements and has been patchily replaced by dolomite, quartz, and pyrite. Rapid chemical and mineralogical variations occur over short distances, i.e. within 10 m. Fe and Mn are both present in greater concentration in dolomite than in calcite. Dolomite itself varies in overall composition within the limestones and dolostones but is always Sr-deficient. The insoluble residue is dominated by quartz. Authigenic quartz occurs but its distribution is controlled by pre-existing detrital quartz so SiO2 distribution corresponds to a detrital arrangement. TiO2 and K2O follow the distribution of SiO2 and are believed to be sited in detrital minerals, muscovite, and other unidentified minerals. Sulphur, present in pyrite, has a patchy distribution but is deficient in totally dolomitized areas suggesting removal of pyrite during dolomitization.

Magnesio-ferri-fluoro-hornblende has the ideal formula A□B Ca2C(Mg4Fe3+)T(Si7Al)O22WF2 (Hawthorne et al., 2012). The holotype sample described in this work occurs as prismatic crystals in vugs of volcanic rocks (Seruci ignimbrites), found along the coast road ∼5.5 km northeast of Portoscuso, Cagliari, Sardinia; associated minerals are tridymite, todorokite, magnetite, and hematite. The name and the mineral were approved by the IMA CNMNC (2014-091). Holotype magnesio-ferri-fluoro-hornblende is monoclinic, space group C2/m, a = 9.839(5), b = 18.078(9), c = 5.319(3) Å, β = 104.99(3)°, V = 913.9(9) Å3, Z = 2. The density calculated from the empirical formula is 3.315 g cm–3. In plane-polarized light, magnesio-ferri-fluoro-hornblende is pleochroic, X = pale grey (least), Y = dark grey (most), Z = pale brownish grey (intermediate); X^ a = 47.6° (β obtuse), Y // b, Z^ c = 33.4° (β acute). It is biaxial negative, α = 1.669, β = 1.676, γ = 1.678, all ±0.002; 2Vobs = 74(1)°, 2Vcalc = 56°. The strongest eight lines in the powder X-ray diffraction pattern are [d in Å (I)(hkl)]: 2.711 (100)(151), 8.412 (89)(110), 3.121 (64)(310), 2.553 (61)(2̄02), 3.389 (55)(131), 2.599 (45)(061), 2.164 (36)(261), and 2.738 (34)(3̄31). Electron-microprobe analysis of the refined crystal gave SiO2 45.34, Al2O3 6.18, TiO2 1.22, FeO 15.24, Fe2O3 6.27, MgO 9.71, MnO 0.78, ZnO 0.06, CaO 10.18, Na2O 1.35, K2O 1.15, F 3.22, Cl 0.30, H2Ocalc 0.37, sum 99.95 wt.%. The empirical formula unit, calculated on the basis of 24 (O, OH, F, Cl) apfu with (OH + F + Cl) = 2 apfu is: (Na0.15K0.22)∑0.37(Na0.25Ca1.66Mn0.09)∑2.00(Mg2.20Fe2+1.94Mn0.01Zn0.01Fe3+0.72Ti0.13)∑5.01 (Al1.11Si6.89)∑8.00O22[F1.55(OH)0.37Cl0.08)∑2.00.

A single crystal of natrojarosite, NaFe3(SO4)2(OH)6, was investigated by single-crystal X-ray diffraction at high-pressure conditions (up to 8.8 GPa) using a diamond-anvil cell. The unit-cell parameters were determined at 11 different pressures and no indications of a phase transition were found up to the maximum pressure reached. The volume and axial moduli were fitted to a third-order Birch–Murnaghan equation-of-state which gave the following values: V0 = 769.6(2) Å3, KT0 = 50.6(9) GPa, K' = 9.9(4); a = 7.3172(6) Å, KT0 = 104(2), K' = 7.6(9); c = 16.5965(20) Å, KT0 = 24.6(4) and K' = 7.1(2). The crystal structure of natrojarosite was refined at seven different pressures up to 8.779(11) GPa [a = 7.3170(4), c = 16.5955(5) Å and V = 769.46(9) Å3 in Rm at 0.00010(1) GPa and a = 7.1594(8), c = 15.6003(17) Å and V = 692.49(8) Å3 at 8.779(11) GPa]. The structural analysis shows that the 12-fold Na polyhedron accommodates most of the deformation by a large volume decrease (14%) and strong polyhedral distortion (63%). Our results indicate that natrojarosite has the most compressible structure of the supergroup studied so far, and has a very strong axial anisotropy.

Electron backscatter diffraction (EBSD) analysis of monazite requires a comparison of empirically collected electron backscatter patterns (EBSPs) with theoretical diffraction data, or ‘match units’, derived from known crystallographic parameters. Published crystallographic data derived from compositionally varying natural and synthetic monazite are used to calculate ten different match units for monazite. These match units are used to systematically index EBSPs obtained from four natural monazite samples with different compositions. Analyses of EBSD data, derived from the indexing of five and six diffraction bands using each of the ten match units for 10,000 EBSPs from each of the four samples, indicate a large variation in the ability of the different match units to correctly index the different natural samples. However, the use of match units derived from either synthetic Gd or Eu monazite crystallographic data yield good results for three of the four analysed monazites. Comparison of sample composition with published monazite compositions indicates that these match units are likely to yield good results for the EBSD analysis of metamorphic monazite. The results provide a clear strategy for optimizing the acquisition and analysis of EBSD data from monazite but also indicate the need for the collection of new crystallographic structure data and the subsequent generation of more appropriate match units for natural monazite.

The previously unknown, complex crystal structures of two fibrous ferric iron phosphate minerals have been solved using single-crystal X-ray diffraction data. The structure of a slightly arsenatian kidwellite has been refined in space group P2/c (a = 20.117(4), b = 5.185(1), c = 13.978(3)Å, β = 107.07(3)°, V = 1393.8(5)Å3, Z = 2) to R1 = 5.21%; a revision of both space group symmetry and chemical formula is proposed. The idealized formula is Na(Fe3+,M)9+x(OH)11(H2O)3(PO4)6, where M = Fe3+, Cu2+ or other metal cation, and x ≈ 0.3. The structure of a slightly arsenatian ‘laubmannite’ (as defined by Moore, 1970) has been refined in space group Pbcm (a = 5.172(1), b = 13.999(3), c = 31.083(6)Å, V = 2250.5(8)Å3, Z = 4) to R1 = 3.14%. The revised, idealized formula is (Fe3+,Fe2+,M)8+x(OH,H2O)9(-H2O)2(PO4)5, where M = Fe3+, Cu2+ or other metal cation, and x ≈ 0.1. The framework structures of both minerals are similar. Dominant building units are dimers composed of face- and edge-sharing FeO6 octahedra. Whereas kidwellite contains an additional trimer built of three corner-sharing FeO6 octahedra, ‘laubmannite’ instead contains a dimer built of two corner-sharing FeO6 octahedra. Kidwellite contains only trivalent iron, while one of the Fe sites in ‘laubmannite’ is occupied by a mixture of Fe3+ and Fe2+ in a 1:1 ratio. In both structures, the FeO6-based building units are linked via corners to PO4 tetrahedra; the M sites are located in narrow channels and have very low occupancies (~2 to 7%) and strongly distorted [6]- or [5+1]-coordinations. Close structural relations between kidwellite and ‘laubmannite’, and other fibrous iron phosphates explain observations of epitaxial intergrowths of them.

Stanleyite, a cobalt-blue mineral, occurs as efflorescent outgrowths on patronite from Cerro de Pasco, Minasragra, Peru. The determined composition is very close to the ideal formula VOSO4.6H2O and yields an empirical formula of V1.01O1.01S0.99O3.99 5.78H2O on the basis of O = 5 in the anhydrous part. X-ray powder data (31 lines) indexed on an orthorhombic cell give a 12.12, b 9.71, and c 14.92Å, cell volume 1755.8Å3 and Z = 8. Refractive indices are α 1.505, β 1.519, and γ 1.533, D is 1.95 (measured) and 2.01 (calculated), H = 1−1½ (Mohs). Thermal analysis and X-ray powder data show stanleyite to be quite different from minasragrite (the pentahydrate) which it clearly mimics. Associated minerals are potassium alum, pyrite, and quartz.