Hematite is a mineral the chemical composition of which rarely differs significantly from stoichiometric Fe2O3. As such, little attention has been paid to the mineral chemistry of hematite in Precambrian iron formations, where hematite forms monomineralic high-grade orebodies. Electron microprobe analysis of hematite from two iron-ore deposits, Cauê (Itabira district) and Gongo Soco, in the Palaeoproterozoic Itabira Iron Formation, Quadrilátero Ferrífero of Minas Gerais, Brazil, has revealed distinct variations in chemical composition with respect to Ti and Cr. Hematite containing Ti and/or Cr is of very local occurrence in the itabirite unit and shows a spatial relationship to hematitic, palladiferous gold-bearing veins (known as ‘jacutinga’), occurring either within the veins (adjacent to, or included in, palladiferous gold grains) or in their vicinity. Where present, titaniferous hematite (to ∼1.3 wt.% TiO2) is lepidoblastic and defines a pervasive tectonic foliation (S1). In contrast, Ti-free, chromiferous hematite (to ∼6.4 wt.% Cr2O3) characteristically occurs as inclusions in palladiferous gold within S1-truncating ‘jacutinga’. Replacement of granoblastic, Ti-free, chromiferous martite with relicts of magnetite by lepidoblastic, Cr-depleted, titaniferous hematite proves that Cr and Ti were mobile during metamorphism. Chromium was ultimately fractionated into the hematite found in auriferous aggregates within cross-cutting ‘jacutinga’. A positive correlation between Cr and Pt in bulk-rock samples from the Itabira district suggests that Cr is a potential prospective guide for Au-Pd-Pt-bearing hematitic veins (‘jacutinga’).

The Cnoc Rhaonastil minor dolerite intrusion on Islay, NW Scotland represents a single body of alkali olivine basalt magma which differentiated in situ, from leucodolerite, through teschenite to minor nepheline syenite. The syenites occur as isolated nests and pegmatitic schlieren within the leucodolerite, and schlieren of gabbroic pegmatite also occur at the margin of the teschenite. The differentiated rocks contain pyroxene, amphibole and biotite of variable compositions which reflect both primary fractionation processes and late-stage deuteric alteration and reaction.Mafic phases within the gabbroic pegmatite, teschenite and syenite are typically rimmed and speckled with biotite, the composition of which is controlled by the local environment of crystallization. The nepheline syenites contain primary ferro-kaersutite which, where in contact with interstitial patches, has been altered to arfvedsonite, which occasionally contains up to 1.2 wt.% ZrO2. The occurrence of Zr-arfvedsonite (and of Zr-aegirine) in interstitial patches suggests that variably trace element-enriched domains existed within the residual melts on very small scales.

The behaviour of ThSiO4 during low-temperature alteration has significance for element mobility and redistribution. Here we describe five types of alteration of ThSiO4 by hydrothermal fluids: (1) primary ThSiO4 associated with chevkinite-(Ce) in a quartz-epidote metasomatite; (2) during alteration of monazite-(Ce) in a quartzolite; (3) during alteration of fergusonite-(Y) in a quartz-epidote metasomatite; (4) following exsolution from chevkinite-(Ce); and (5) associated with cerite-(Ce) and with ilmenite and bastnäsite-(Ce) in late-stage veinlets in a syenitic pegmatite and a metasomatite. The great majority of crystals have been strongly altered compositionally, with variable degrees of replacement of formula elements by non-formula elements, such as Ca, Fe, P and REE. The most reliable geochemical indicators of hydrothermal alteration are low analytical totals and non-stoichiometric structural formulae. The alteration is variably ascribed to dissolution-reprecipitation and pervasive fluid infiltration along cracks. Thorium appears to have shown limited mobility in these samples.

Three natural crystals of the wulfenite (PbMoO4)—stolzite (PbWO4) series were investigated by single-crystal X-ray diffraction. The results indicate that the symmetry is I41/a from nearly pure wulfenite to intermediate compositions, in contrast to previous work which claimed a symmetry change to 74 symmetry (acentric) for intermediate compositions compared with I41/a (centric space group) for the end-members. The results reported here show that the reflections violating I41/a symmetry observed in this work and in a previous study are related primarily to λ/2 effects, even if Renninger effects are not excluded. Consequently, we find that the I41/a symmetry is retained throughout the wulfenite— stolzite.

A recent investigation of sphalerite from Akoluk deposit, Ordu, NE Turkey, revealed the possible presence of a new activator element in the sphalerite structure. The sample was studied under a reflected light microscope coupled with a cold-stage cathodoluminescence (CL) system which revealed a unique banding in the sphalerite. The same sample was subsequently examined using the backscattered electron and luminescence modes in an electron microscope, the results of which were later confirmed in terms of chemical composition by electron probe microanalyses (EPMA). Detailed evaluation of the EPMA data indicated the presence of a new CL activator element in the sphalerite structure. The data also indicate that Hg2+ in the sphalerite crystal structure substitutes for Zn in a simple manner and for Cd and Cu in a coupled manner. Spectral analysis indicated a bright yellow and orange-red blend (more like brown) CL colour with λmax centred at 580 nm, probably due to Cd and Mn ions, and relatively broad emission bands ranging from 525 to 690 nm with λmax centred at 580 and 700, due probably to Cu, Cd and Hg. This study reports that Hg in the sphalerite crystal lattice behaves as an activator and/or co-activator element resulting in emissions of CL colours that range from yellow with purple shades to shades of brown, based on their varying contents.

Silicate minerals enriched in V, Cr and Mn including garnets and epidote-supergroup members, in association with amphiboles, albite, hyalophane, titanite, chamosite, sulfides and other minerals occur in Devonian black shales near Čierna Lehota in the Strážovské vrchy Mountains, Slovakia. The garnets have high concentrations of V, Cr and Mn (up to 17 wt.% V2O3, ≤11 wt.% Cr2O3 and ≤ 21 wt.% MnO) and several compositional types. Vanadian-chromian grossular (Grs 1) usually preserves primary metamorphic oscillatory zoning, whereas solid solutions between goldmanite (Gld 2A,B), V- and Cr-rich grossular and spessartine (Grs 2A,B, Sps 2) form irregular domains or crystals with variable zoning. Dominant substitutions in the garnets include CaMn–1 and (V,Cr)Al–1, resulting in coupled Ca(V,Cr)Mn–1Al–1. Epidote-supergroup minerals occur as abundant anhedral crystals with variable compositional zoning. Nearly all crystals have a complete zoning sequence beginning with REE-rich allanite-(La), followed by mukhinite and by V- and Cr-rich clinozoisite to mukhinite and V- and Cr-poor clinozoisite. In common with garnets, the epidote-supergroup minerals are enriched in V, Cr and Mn (<7 wt.% V2O3, <5 wt.% Cr2O3 and <3 wt.% MnO). Lanthanum is the dominant REE (up to 11.5 wt.% La2O3) in allanite-(La). The composition of epidote-supergroup minerals is controlled by REEFe2+(CaAl)–1, REEMg(CaAl)–1, REEMn2+(CaAl)–1 and REEFe2+(CaFe3+)–1 substitutions introducing REE, together with VAl–1 and CrAl–1 substitutions. The negative Ce and slightly positive Eu anomalies displayed in chondrite-normalized patterns and enrichment in V, Cr and Mn are ascribed to the geochemical properties of the protolith. The minerals investigated exhibit multi-stage evolution: (1) presumed low-grade greenschist-facies metamorphism; and (2) development of V- and Cr-rich zones in both garnet- and epidote-supergroup minerals which result from late-Variscan contact metamorphism due to granitic intrusion of the Suchý Massif. Decreased temperature following the metamorphic peak probably resulted in the formation of REE-, V- and Cr-poor clinozoisite and secondary garnet.

Hloušekite, (Ni,Co)Cu4(AsO4)2(AsO3OH)2(H2O)9, is a new supergene arsenate mineral from the Geister vein (Rovnost mine), Jáchymov (St Joachimsthal), Western Bohemia, Czech Republic. It was found along with veselovský ite, pradetite, lavendulan, arsenolite, babánekite and gypsum on the surface of strongly altered ore fragments containing dominant tennantite and chalcopyrite. Hloušekite forms thin, lath-like crystals, locally elongated reaching up to 3 mm across. It is transparent, has a pale green colour with vitreous lustre, has a greyish-white streak and it is very brittle with an uneven fracture. It does not fluoresce under shortwave or longwave ultraviolet radiation. Cleavage on {010} is perfect; the Mohs hardness is 2–3. The calculated density is 3.295 g cm–3. Hloušekite is optically biaxial with α’ = 1.653(2) and γ’ = 1.73. The estimated optical orientation is γ’ vs. elongation (c) = 14(1)°. In larger grains it is weakly to moderately pleochroic (α = colourless, γ = pale green to green). Hloušekite is triclinic, space group P, a = 6.4010(6), b = 8.0041(6), c = 10.3969(14) Å , α = 85.824(8), β = 79.873(9), γ = 84.655(7)° and V = 521.23(10) Å3, with Z = 1, a:b:c = 0.800:1:1.299. The eight strongest lines in the powder X-ray diffraction (XRD) pattern [d in Å (I)(hkl)] are 10.211(100)(001), 7.974(9)(010), 3.984(6)(020), 3.656(5)(12), 3.631(5)(01), 3.241(5)(022), 3.145(5)(200) and 3.006(5)(210). Chemical analysis by electron microprobe yielded MgO0.20, FeO0.10, NiO 5.79, CoO1.80, CuO29.53, ZnO 0.66, Al2O3 0.14, P2O5 0.11, As2O5 45.01, H2O 17.71 (calc.), for a total of 101.05 wt.%. The resulting empirical formula, calculated by stoichiometry (9H2O + 2OH), obtained from the crystal structure, is (Ni0.79Co0.25)Σ1.04(Cu3.78Zn0.08Mg0.05Al0.03Fe0.01)Σ3.95 (AsO4 )1.98(PO4 )0.02(AsO3OH)2.00(H2O)9.00 . The ideal endmember formula , NiCu4(AsO4)2(AsO3OH)2(H2O)9.00, requires NiO7.23, CuO30.81, As2O5 44.51, H2O17.45, total 100.00 wt.%. The crystal structure of hloušekite was solved by charge flipping from single-crystal XRD data and refined to R1 = 0.0599 for 1441 reflections with [Iobs > 3σ(I)]. Hloušekite is a new member of the lindackerite group (also including lindackerite, pradetite and veselovský ite) of the lindackerite supergroup. The ondrušite group of the lindackerite supergroup includes ondrušite, chudobaite, geigerite and klajite. The establishment of these two groups reflects the difference between the crystal structures of their members, mainly in the coordination environment of the Me cations.

We report the crystal structures of eight new synthetic multinary Rb–Cu sulfates representing four new structure types: δ-Rb2Cu(SO4)2, γ-RbNaCu(SO4)2, γ-RbKCu(SO4)2, Rb2Cu2(SO4)3, Rb2Cu2(SO4)3(H2O), β-Rb2Cu(SO4)Cl2, β-Rb4Cu4O2(SO4)4⋅(Cu0.83Rb0.17Cl) and Rb2Cu5O(SO4)5. The determination of their crystal structures significantly expands the family of anhydrous copper sulfates. Some of the anhydrous rubidium copper sulfates obtained turned out to be isostructural to known compounds and minerals. Rb2Cu5O(SO4)5 is isostructural to cesiodymite, CsKCu5O(SO4)5 and cryptochalcite, K2Cu5O(SO4)5. Rb2Cu2(SO4)3 also shows an example of crystallisation in the already known structure type first observed for synthetic K2Cu2(SO4)3. ‘Hydrolangbeinite’, Rb2Cu2(SO4)3(H2O), was formed as a result of a minor hydration of the initial mixture of reagents.

The minerals and synthetic framework compounds of the A2Cu(SO4)2 series demonstrate a vivid example of morphotropism with the formation of structural types depending on the size of the cations residing in the cavities of the [Cu(SO4)2]2– open framework. To date, five types (α, β, γ, δ and ε) can be distinguished. We propose to call this series of compounds ‘saranchinaite-type’, as the stoichiometry A2Cu(SO4)2 was first encountered during the discovery and description of saranchinaite, Na2Cu(SO4)2.

The discovery of β-Rb2Cu(SO4)Cl2, a new monoclinic polymorph of chlorothionite, seems to be of particular interest considering the recently discovered interesting magnetic properties of synthetic K2Cu(SO4)X2 (X = Cl and Br) and Na2Cu(SO4)Cl2.

In these new structural architectures, a number of features have been revealed that were seldom observed previously. The first is the bidentate coordination of the sulfate tetrahedron via edge-sharing with the Cu2+-centred coordination polyhedron. Until recently, such coordination was known only for the chlorothionite structure. The second is formation of ‘high-coordinate’ CuO7 polyhedra. The structures of the new compounds suggest that such coordination is not in fact so uncommon, at least among anhydrous alkali copper sulfates. All of the described features clearly indicate the importance of further systematic studies of anhydrous copper-sulfate systems. Their exploration, particularly of the new copper-oxide substructures with new coordination environments, is highly likely to lead to new potentially interesting magnetic properties due to the unusual arrangements of magnetically active Cu2+ cations.

In addition to experimental details on the synthesis of rubidium analogues of anhydrous potassium and sodium sulfates, this work also provides an analysis and a brief review of the geochemistry of rubidium in volcanic environments.

In contrast with some other hydrous aluminum phosphates, vashegyite is crystalline. Simultaneous application of several assumptions leads to the hypothesis that it has a structure analogous to that of kaolinite, and thus contains tetrahedral sheets, n[X2O5], where X is both P and H3 (in lieu of Si). Thus, the theory involving [HXO4] is extended from phosphates with isolated tetrahedral groups [XO4] and framework linkages [XO2] to sheet linkages [X2O5]. Kingite also may have a kaolinite-like structure.

Pd-rich PGM (platinum-group minerals) have been found in sulphide-bearing dunites and harzburgites from the Inazumi-yama ultramafic complex in southwestern Japan. In the dunite, potarite (PdHg0.85–0.88) is the most abundant PGM but other associated PGM include stibiopalladinite (Pd5Sb2) and rare sperrylite (PtAs2) and Pd-rich alloys. A Pd telluride has been found in the harzburgite. The PGM are enclosed usually by pentlandite-heazlewoodite composite grains and, rarely, by altered chrome-spinel. These minerals are characteristic of an ultramafic assemblage but they are accompanied by ubiquitous galena and minor sphalerite not usually associated with these ultramafic assemblages. The ultramafic part of this complex has been thermally metamorphosed (olivine-talc zone) within the contact aureole of an adjacent granite. The PGM, sulphides and altered spinel are all intergrown with antigorite and/or chlorite, indicating a metamorphic overprint on the primary igneous mineralogy. The Pd/Pt ratios of 9 suggest a process of hydrothermal concentration for the Pd and it is proposed that the Pd has been remobilized and reconcentrated by hydrothermal solutions derived from the granitic magma which reacted with the Pd concentrated in the primary magmatic sulphides. Mercury may have been leached from surrounding sediments by the hydrothermal solutions. It is possible that potarite and the other PGM formed at temperatures of up to 650°C and are likely to be found in other thermally metamorphosed ultramafic rocks showing a depleted character (spinel Cr/[Cr+Al]>0.7), common in orogenic belts.

Found at the Joe and Grand Central mines, Tombstone, Arizona, USA, in quartz gangue with girdite, rodalquilarite, bromargyrite, and gold. Crystals orthorhombic, tabular to scaly on {010} up to 1 mm; H = 2, colour white, Dmeas = 4.98 ± 0.12.

Chemical analysis gave PbO 58.2 %, TeO3 28.6, SO3 6.8, H2O 4.7. Easily fusible to red-brown slag and soluble in cold, dilute acids.

Crystals orthorhombic Cmcm; a = 9.67 Å, h = 19.56, c = 10.47. Strongest lines 9.778 (10), 3.426 (6), 3.250 (6B), 3.560 (5B), 3.338 (5), 3.033 (5), 2.934 (5), 2.603 (5). Dcalc = 5.15, Z = 16. Indices are α = 1.897, β = 1.940, γ = 1.942, 2Va = 24°; γ‖a, α‖b, β‖c.

The mineral and name have been approved by the Commission on New Minerals and New Mineral Names, IMA.

A suite of coarsely crystalline samples of crinoidal limestone adjacent to a PbS-CaF2-CaCO3 vein in the North Pennine orefield (Greenhow Rake) was analysed by three independent methods [Inductively Coupled Plasma emission spectroscopy (ICP), Mass Spectrometry (MS) and Gas Chromatography (GC)], in order to determine the nature and origin of trace elements and volatiles released on heating and thermal decrepitation, to establish whether fluid inclusions from the host limestone differed in composition from those within the vein, and to assess the value of the results obtained for mineral exploration. The ICP method gave reproducible results for Ca, Na and K, and significant values for Pb and Zn. Na and K correlate with H2O levels determined by MS/volumetric analysis, suggesting their coexistence within fluid inclusions. No such correlation was found for Pb and Zn, suggesting that these elements were derived by volatilisation, perhaps from traces of galena and sphalerite. Methane showed no correlation with H2O and a source other than aqueous fluid inclusions is thought probable for this volatile.

The vein calcite showed much lower K/Na fluid ratios (0.05 cf 0.1–0.2), than the limestones. The limestone-hosted fluids occur predominantly in crinoid ossicles and are believed to represent early pre-mineralisation fluids, unrelated to those associated with veining. Combined ICP and MS techniques may be of value in investigating samples where fluid inclusions are too small for microthermometric and optical analysis.

A new mineral species, vigezzite (Ca,Ce) (Nb,Ta,Ti)2O6, was found near Orcesco, Valle Vigezzo, Prov. Novara, Northern Italy. It forms fiat prismatic crystals up to 2–3 mm length of an orange-yellow colour. The crystals are elongated along the a-axis and flattened on (010). Cleavage at right angles to the prism axis is distinct, fracture conchoidal. Vickers hardness VHN = 396 kp/mm2, corresponding to in the Mohs scale. Refraction indices are high: α = 2.14, γ = 2.315 (NaD, 589 µm), birefringence is 0.175. Optic angle 2Vγ is large. Though intensively yellow coloured, the mineral shows no pleochroism. α = c, β = b, γ = a; optic axial plane is parallel to (010).

Vigezzite is orthorhombie with space group Pmnb or P21nb; a = 7.559±0.01, b = 11.028±0.01, c = 5.360± 0.004 Å, Z = 4. The six strongest lines of the X-ray powder pattern are 4.821 (9) (011), 3.784 (8) (200), 3.036 (10) (031), 2.974 (10) (211), 1.7129 (6) (242), 1.6018 (7) (431).

Electron microprobe analyses lead to the empirical formula (Ca0.82Ce0.24)Σ1.06(Nb0.9Ta0.62Ti0.5)Σ2.02O6. The mineral is not completely homogenous, the ratio Nb/(Nb+Ta) varies from 0.55–0.62. Rynersonite Ca (Ta,Nb)2O6, may represent the Ta-dominant equivalent of vigezzite. Vigezzite occurs together with several other Nb-minerals such as pyrochlore, columbite and fersmite, whose crystallographical and chemical data are reported, in an albitic rock of presumably pegmatitic origin.

The effect of competition from other metal ions on the complexation of Ni with isosaccharinic acid, gluconic acid and picolinic acid, at high pH, is described. The competing metal ions used were divalent Co, trivalent Eu and tetravalent Th. In the majority of cases, competition from these metal ions followed the predicted pattern, with most anomalies seeming to be caused by sorption of Ni to the many different solid phases formed in presence of the competing ions. The Ni solid phase was shown to change with time during the course of the study. No major unexplained competition effects were found.

Volcanic activity at Mt Vulture lasted throughout the Middle Pleistocene and produced SiO2- undersaturated volcanics. Deposits from the Monte Vulture stratovolcano have been classified into four subsynthems and clustered into the Barile Synthem. In the present investigation, trioctahedral micas from the uppermost units (the Ventaruolo Subsynthem) of the Barile Synthem are considered. The samples are labelled VUT187. The phlogopitic micas were separated from the host rock (an olivinefoidite) and underwent chemical (electron microprobe analysis - EMPA and C-H-N), structural (singlecrystal X-ray diffraction) and spectroscopic (Mössbauer) investigations.

The EMPA yielded: MgO (17.62–21.89 wt.%), FeOtot (5.98–9.78 wt.%), TiO2 (1.81–3.92 wt.%) and Al2O3 (14.47–17.98 wt.%), with H2O contents = 2.86 (±0.42) wt.% determined by C-H-N analyses. Mössbauer investigation provided [VI]Fe2+ = 12.6%, [VI]Fe3+ = 87.4%. The chemical and structural data are consistent with the occurrence of Ti-oxy, [VI]M2+ + 2(OH)– ⇋ [VI]Ti4+ + 2O2– + H2, and M3+-oxy substitutions, [VI]M2+ + (OH)– ⇋ [VI]M3+ + O2– + 1/2H2, with M3+ = Fe3+, Al3+. In particular, Fe3+-oxy substitution has affected the Fe2+/Fe3+ ratioin the studied sample. This is probably due to the fact that interaction with underground water or a hydrothermal system may have altered the oxygen fugacity and raised the Fe3+ content of VUT187 phlogopite with respect to magmatic values.

Auroselenide, ideally AuSe, is a new mineral from the Gaching ore occurrence of the Maletoyvayam deposit, Kamchatka peninsula, Russia. It occurs as anhedral grains up to 0.05 × 0.02 mm and as intergrowths up to 0.06 mm with maletoyvayamite–tolstykhite-series minerals, enclosed in native gold. Other associated minerals include pyrite, calaverite, fischesserite, gachingite, tetrahedrite-group minerals [stibiogoldfieldite, its As-analogue, tennantite-(Cu) and tetrahedrite-(Zn)], tripuhyite, minerals of the famatinite–luzonite and selenium–tellurium series, paraguanajuatite, petrovskaite, součekite and tiemannite. Auroselenide is bluish-grey, opaque with metallic lustre and grey streak. It is brittle and has an uneven fracture. Dcalc = 9.750 g/cm3. In reflected light, auroselenide is grey with a bluish shade. Bireflectance is very weak. No pleochroism and internal reflections are observed. In crossed polars, it is strongly anisotropic with bluish to brownish rotation tints. The reflectance values for wavelengths recommended by the Commission on Ore Mineralogy of the International Mineralogical Association are (Rmin/Rmax, %): 28.4/31.5 (470 nm), 30.2/33.3 (546 nm), 31.9/34.9 (589 nm) and 34.3/37.3 (650 nm). The principal bands in the Raman spectrum of auroselenide are at 93, 171, 200, 210 and 325 cm–1. The empirical formula calculated on the basis of 2 atoms per formula unit is (Au0.98Ag0.01)Σ0.99(Se0.79S0.17Te0.05)Σ1.01. Auroselenide is monoclinic, space group C2/m, a = 8.319(1), b = 3.616(1), c = 6.276(2) Å, β = 104.54(2)°, V = 182.74(5) Å3 and Z = 4. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 4.015 (54) (200); 3.033 (25) (${\bar 1}$11, 002); 2.780 (100) (${\bar 2}$02, 111); 2.172 (20) (${\bar 3}$11, 310); and 1.811 (25) (${\bar 1}$13). Auroselenide is the natural analogue of synthetic β-AuSe. The structural identity between them is confirmed by powder X-ray diffraction and Raman spectroscopy. The mineral is named according to its composition, as a combination of the main elements Au (aurum) and Se (selenium).

There are many basic copper chlorides and sulphates which occur as minerals but have received little recent crystallographic study. Yet copper is a widely distributed element and many of these minerals are the products of corrosion and weathering of bopper and copper ores.

In 1948 we were able to confirm the earlier goniometric work of G. F. Herbert Smith (1906) that paratacamite and atacamite are not identical species (Max H. Hey, 1950) and showed that the two minerals give different X-ray powder patterns. This result was further extended by Clifford Frondel (1950) to a single 'crystal and thermal study of paratacamite, in the course of which he measured the rhombohedral unit-cell dimensions and showed that this mineral can be artificially produced by various methods as well as by the action of salt-water on copper.