The mode of occurrence of uraninite, pitchblende and coffinite at five localities in south-west England is described. Chemical and isotopic analyses of concentrates containing these minerals provide the following 206Pb/238U ages (My.): uraninite, South Crofty, Cornwall, 277 ± 10; uraninite, Geevor, Cornwall, 223 ± 5; pitcbblende-coffinite, King's Wood, Devon, 206 ± 5; pitchblende, Wheal Bray, Cornwall, 165 ± 4; pitchblende, South Terras, Cornwall, 474 ± 2; coffinite, Geevor, Cornwall, c. 45 (chemical analysis only). These results are compatible with geological and mineralogical evidence. Consideration of these and other results indicates that there were at least three periods of uranium mineralization in south-west England, at c. 290 My., c. 225 My., and c. 50 My. Other intermediate ages may also be valid but further work is required to substantiate these.

Two quintinite polytypes, 3R and 2T, which are new for the Kovdor alkaline-ultrabasic complex, have been structurally characterized. The crystal structure of quintinite-2T was solved by direct methods and refined to R1 = 0.048 on the basis of 330 unique reflections. The structure is trigonal, P$\bar 3$c1, a = 5.2720(6), c = 15.113(3) Å and V = 363.76(8) Å3. The crystal structure consists of [Mg2Al(OH)6]+ brucite-type layers with an ordered distribution of Mg2+ and Al3+ cations according to the $\sqrt 3 $ × $\sqrt 3 $ superstructure with the layers stacked according to a hexagonal type. The complete layer stacking sequence can be described as …=Ab1C = Cb1A=…. The crystal structure of quintinite-3R was solved by direct methods and refined to R1 = 0.022 on the basis of 140 unique reflections. It is trigonal, R$\bar 3$m, a = 3.063(1), c = 22.674(9) Å and V = 184.2(1) Å3. The crystal structure is based upon double hydroxide layers [M2+,3+(OH)2] with disordered distribution of Mg, Al and Fe and with the layers stacked according to a rhombohedral type. The stacking sequence of layers can be expressed as …=АB = BC = CA=… The study of morphologically different quintinite generations grown on one another detected the following natural sequence of polytype formation: 2H → 2T → 1M that can be attributed to a decrease of temperature during crystallization. According to the information-based approach to structural complexity, this sequence corresponds to the increasing structural information per atom (IG): 1.522 → 1.706 → 2.440 bits, respectively. As the IG value contributes negatively to the configurational entropy of crystalline solids, the evolution of polytypic modifications during crystallization corresponds to the decreasing configurational entropy. This is in agreement with the general principle that decreasing temperature corresponds to the appearance of more complex structures.

A new mineral katiarsite, ideally KTiO(AsO4), occurs in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with hatertite, bradaczekite, johillerite, yurmarinite, tilasite, arsmirandite, hematite, tenorite, As-bearing orthoclase, fluorophlogopite and aphthitalite. Katiarsite occurs as long prismatic to acicular, typically sword-like, crystals up to 3 μm×10μm×50 μm in size, and rarely up to 0.15 mm long. Crystal forms are {011}, {201}, {100} and {001}. Katiarsite is transparent, colourless, with a vitreous lustre. The mineral is brittle. Cleavage was not observed, the fracture is uneven. Dcalc is 3.49 g cm–3. Katiarsite is optically biaxial (+), α = 1.784(3), β = 1.792(3), γ = 1.870(5); 2Vobs is small. Orientation is X = b, Y = a, Z = c. The Raman spectrum is reported. The chemical composition (wt.%, electron-microprobe data) is K2O 18.98, Fe2O3 5.07, TiO2 27.49, As2O5 47.48, total 99.02. The empirical formula, calculated based on 5 O apfu, is K1.00 (Ti0.85Fe3+0.16)∑1.01 As1.02O5. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are 5.91(17)(110), 5.62(74)(011), 4.18(19)(202), 3.157(66) (013), 2.826(100)(221), 2.809(96)(022) and 2.704(19)(004). Katiarsite is orthorhombic, a = 13.174(4), b = 6.5635(10), c = 10.805(2) Å, V = 934.3(3) Å3, Z = 8, space group Pna21, by analogy with KTA, synthetic KTiO(AsO4), a notable non-linear optical crystalline material. The name of the mineral reflects its chemical composition, kalium titanyl arsenate.

A nomenclature and classification scheme has been approved by IMA–CNMNC for the magnetoplumbite group, with the general formula A[B12]O19. The classification on the highest hierarchical level is decided by the dominant metal at the 12-coordinated A sites, at present leading to the magnetoplumbite (A = Pb), hawthorneite (A = Ba) and hibonite (A = Ca) subgroups. Two species remain ungrouped. Most cations, with valences from 2+ to 5+, show a strong order over the five crystallographic B sites present in the crystal structure, which forms the basis for the definition of different mineral species. A new mineral name, chihuahuaite, is introduced and replaces hibonite-(Fe).

Ettringite was the name given by J. Lehmann in 1874 to minute, transparent, acicular crystals lining the cavities of metamorphosed limestone-inclusions in leucite-nepheline-tephrite from the Ettringer-Bellerberg, near the village of Ettringen (between Mayen and the Laacher See), Rhineland. Lehmann detached sufficient needles from the limestone for chemical analysis, and found that they were not gypsum, as formerly supposed, but a hydrated calcium sulphoaluminate.

Recognition of widespread carbonate volcanism in central Spain has led to another case in France, of similar age (23–0 Ma) but with entirely new features. More than 100 new carbonate volcanoes are indicated already, adding a wholly unexpected dimension to this form of activity. Eruptions form layers, mostly of glassy nephelinite fragments in a dolomitic matrix, but some layers are largely dolomite. Major new findings are phenocrysts of dolomite, magnesite and calcite in silicate glass, and spectacular dolomite-nephelinite melt immiscibility, neither recorded previously. Most volcanic carbonatites are Ca rich, and dolomite is rare. The Limagne dolomites share links with those in Spain and Zambia, with chromite a hallmark in all three. Limagne is exceptional in being the first case where dolomite has erupted with co-genetic silicate melt. Mantle debris and magnesite indicate a source within ∼ 100–150 km. Chromite in the dolomite globules, and in the enclosing silicate glass, is similar to that in high-temperature kimberlites, indicating immiscibility in the deep mantle. Recognition of two large, previously undetected provinces of carbonate volcanism in Europe, where there has been active research for >200 y, must lead to the inference that similar cases may await discovery on other continents.

A new mineral, yaroshevskite, ideally Cu9O2(VO4)4Cl2, occurs in sublimates collected from the Yadovitaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with euchlorine, fedotovite, hematite, tenorite, lyonsite, melanothallite, atlasovite, kamchatkite and secondary avdoninite, belloite and chalcanthite. Yaroshevskite forms isolated prismatic crystals, up to 0.1 × 0.15 × 0.3 mm in size, on the surface of euchlorine crusts. The mineral is opaque and black, with a reddish black streak and lustre between metallic and adamantine. Yaroshevskite is brittle, no cleavage was observed and the fracture is uneven. The Mohs hardness is ~3½ (corresponding to a mean VHN micro-indentation hardness of 172 kg mm -2) and the calculated density is 4.26 g cm-3. In reflected light, yaroshevskite is grey with a weak bluish hue. Pleochroism, internal reflections and bireflectance were not observed. Anisotropy is very weak. The composition (wt.%) determined by electron microprobe is: CuO 61.82, ZnO 0.53, Fe2O3 0.04, V2O531.07, As2O50.32, MoO3 1.56, Cl 6.23, O=Cl2 1.41; total 100.16. The empirical formula, calculated on the basis of 20 (O + Cl) anions is (Cu8.80 Zn0.07 Fe0.01)Σ 8.88(V3.87Mo0.12As0.03)σ 4.02O18.01Cl1.99. Yaroshevskite is triclinic, space group P, a = 6.4344(11), b = 8.3232(13), c = 9.1726(16) Å , α = 105.338(14), β = 96.113(14), γ = 107.642(1)°, V = 442.05(13) Å3 and Z = 1. The nine strongest reflections in the X-ray powder pattern [dobs in Å (I)(hkl)] are as follows: 8.65(100)(001); 6.84(83)(01); 6.01(75)(100); 5.52(60)(01); 4.965(55)(011); 4.198(67)(1); 4.055(65)(110); 3.120(55)(021); 2.896(60)(21,003,20). The crystal structure was solved by direct methods from single-crystal X-ray diffraction data and refined to R = 0.0737. The yaroshevskite structure is unique. It is based on corrugated layers made up of chains of edge-sharing flat squares with central Cu2+ cations [Cu(1), Cu(4) and Cu(5)]; neighbouring chains are connected via groups consisting of three Cu2+ -centred squares [two Cu(3) and Cu(6)]. Neighbouring layers are connected via pairs of Cu(2)O4Cl five-coordinate polyhedra and isolated VO4 tetrahedra. The structure of yaroshevskite can also be considered in terms of oxygen-centred tetrahedra: O(7)Cu4 tetrahedra are connected via common Cu(4) and Cu(5) vertices to form pyroxene-like chains [O2Cu6]∞. In this context, the structural formula can be written Cu3[O2Cu6][VO4]4Cl2. The mineral name honours the Russian geochemist Alexei A. Yaroshevsky (b. 1934) of Moscow State University.

Mineralogical and chemical data are presented on an intrusion of a hypersthene gabbro body into coarse-grained noritic cumulates of the critical zone, which occurs at the margin of the Rustenburg Layered Suite of the Bushveld Complex. Two types of contact relations are found between the above two rock suites: (1) a clearly cross-cutting contact is observed on the southern margin of the hypersthene gabbro body close to the interface between the layered suite and the floor rocks; (2) a diffuse heterogeneous contact is found on the north-western limb of the body which is further into the complex. Field observations and chemical data suggest that, at the time of the hypersthene gabbro injection, the surrounding cumulates were above ambient temperatures. The difference in the contacts described above is probably related to the prevailing temperature gradient at the time of emplacement. The cumulate rocks further into the complex were at a higher temperature than those closer to the margin.

Trace element chemistry and phase relations in the basalt tetrahedron indicate that the hypersthene gabbro is genetically unrelated to the cumulate rocks which it intrudes. The body probably represents an offshoot of the magma from which the upper zone of the Rustenburg Layered Suite crystallized.

Small (<2 km diameter), ultramafic intrusive complexes in the Andriamena region of Madagascar contain zones with disseminated chromite and sulphides which carry high concentrations of platinum-group elements (PGE). Assay of drill core from one complex, designated UM2, revealed three zones showing consistently high PGE grades. Mineralogical investigation of the UM2 core reveals that a small number of low reflecting, Pd-bearing platinum-group minerals (PGM) are present — always in association with a poorly characterized Pd stibio-arsenide [Pd3(Sb,As)] phase — in the shallowest of the three zones. Electron microprobe analysis of these PGM indicates the presence of oxygen and that at least two species exist. The resulting stoichiometries suggest that at least one species could be a hydrated form of palladinite [PdO.(H2O)n]. The other phase could be a hydroxide [Pd(OH)2] or a less strongly hydrated form of palladinite. Textural evidence suggests that the Pd-O species formed via the replacement of a precursor Pd-rich PGM, with only a limited removal of Pd, rather than via precipitation of a Pd-O PGM from a fluid that was Pd-bearing. The limited thermal stability of hydrated Pd oxides and the apparent restriction of the Pd-O phases to a shallow zone which is affected by the seasonal movement of groundwater, suggests that they may have formed at low temperatures via the leaching and replacement of other elements from a precursor Pd-rich PGM by oxygen and water during alternating water-saturated and dry conditions. If this is the case, the water table interface might be another environment, in addition to the surface, in which to look for the development of PGE oxides.

The island of São Vicente has the most abundant carbonatite outcrops in the Cape Verde Islands. A field survey of the main outcrops has shown that they consist of extrusive carbonatites, carbonatite dykes and small apophyses of intrusive carbonatite. These outcrops are spatially related to nephelinites. The compositions of the extrusive carbonatites and dykes plot close to, and within, the magnesiocarbonatite field. In contrast, the intrusive carbonatites are calciocarbonatites, with similar average strontium contents to those of extrusive carbonatites and dykes (around 4000 ppm), but remarkably low barium, niobium and total rare earth element concentrations. Whole-rock geochemistry indicates a strong affinity between the nephelinites and intrusive carbonatites, such that the latter could represent fractionation products of the same parental magma. This is in agreement with radiogenic isotope geochemistry, which shows a very restricted range of compositions in the Sr, Nd and Pb systems. Fractionation from a common parental magma occurred in two main steps: high-temperature nephelinite crystallization and high-temperature carbonatite immiscibility. The carbonatitic melts crystallized in two different environments, as follows: (1) a shallow intrusive environment, giving rise to the early calciocarbonatite cumulates; and (2) a vapour-dominated, extrusive environment, producing the later magnesiocarbonatites.

Archerite, (K, NH4)H2PO4, a new mineral, has been found in Petrogale Cave, 36 km east of Madura Motel (31° 54′S, 127°00′E) Western Australia. Archerite and biphosphammite together with aphthitalite, halite, syngenite, stercorite, oxammite, weddellite, whitlockite, guanine, newberyite, calcite, (NH4)2Ca(HPO4)2·H2O, and an unknown occur as stalactites and wall and floor crusts.

Archerite is tetragonal with second order prisms and pyramids in crystals up to 2 mm in length with D 2·23, ω 1·513, ε 1·470, all close to artificial KH2PO4. The mineral is soft, has a white streak, and is soluble in cold H2O. Cell dimensions of natural archerite were not determined and the composition was calculated from measurements of selected powder lines correlated with charts prepared from end-member data and by chemistry which gave 81% KH2PO4 and K2O 10·8, NH2 3·46 respectively, the latter corresponding to (K0·74(NH4)0·26)H2PO4.

The name is for Dr. M. Archer, Curator of Mammals, Queensland Museum. Type material is stored in the collections of the Government Chemical Laboratories, Perth, Western Australia.

Glass-ceramics based on the mineral cordierite have good mechanical and thermal properties. They can be easily prepared from glasses whose compositions lie in the primary phase field of cordierite on the 5 % CaO plane of the CaO-MgO-SiO2-Al2O3 system. For uniform crystallization in the bulk, addition of a suitable nucleating agent is essential. The addition of 10–12 wt % of TiO2 is considered to be suitable for both ternary and quaternary glasses. During controlled heat treatment of these glasses extensive phase separation occurs. The nucleation and crystallization processes that follow have been studied by differential thermal analysis, X-ray diffraction, and light and electron microscopy. Some of the physical and mechanical properties of these glass-ceramics have been measured.

Synthesis of large zeolite A and X crystals by a modified Charnell’s method led to the formation of twinned zeolite NaA crystals, overgrowth of NaX onto NaA and co-crystallization of another phase analysed by electron microprobe as a Na aluminosilicate but not yet identified. Single crystals of NaA have a perfect cubic habit with a 100 μm edge. Twinned crystals of NaA are of the same size and correspond to an intergrowth of two cubes like that found in twinned fluorite crystals. NaX single crystals are octahedral, 220 μm along the [100] direction. Based on the difference in morphology of A and X crystals, epitaxial growth of NaX zeolite on NaA was also clearly identified by scanning electron micrographs. The object of this contribution is to provide topological and structural information on the twinning and epitaxy.

Ruatapu cave has developed beneath a block of hydrothermally altered Quaternary vitric tuff in the active Orakei Korako geothermal field. The cave extends ∼45 m, with a vertical drop of 23 m, to a shallow pool of clear, sulfate-rich (∼.450 µg/g), warm (T = 43–48°C), acid (pH = 3.0) water. Steam, accompanied by H2S, rises from the pool surface, from a second pool nearby, and from fumaroles and joints in the ignimbrite, to condense on surfaces within the cave. Oxidation of the H2S to H2SO4 produces acid sulfate fluids which react with the surficial rocks to generate three principal and distinct assemblages of secondary minerals. Kaolinite ± opal-A ± cristobalite ± alunite ± alunogen dominate the assemblage at the cave mouth; the essential Al, K and Si are derived from the tuffs and Na, Ca, Fe and Mg removed. In the main body of the cave the highly limited throughflow of water results in the more soluble of the leached constituents, notably Na and K, being retained in surface moisture and becoming available to form tamarugite and potash alum as efflorescences, in part at the expense of kaolin, along with lesser amounts of alunogen, meta-alunogen, mirabilite, halotrichite, kalinite, gypsum and, possibly, tschermigite; the particular species being determined by the prevailing physico-chemical conditions. Heat and moisture assist in moving Fe out of the rock to the air-water interface but, unlike typical surficial acid alteration systems elsewhere in the TVZ, there is an insufficient flow of water, of appropriate Eh-pH, to continue to move Fe out of the cave system. Much becomes locally immobilized as Fe oxides and oxyhydroxides that mottle the sides and roof of the cave. Jarosite crusts have developed where acid sulfate pool waters have had protracted contact with ignimbrite wallrock coated with once-living microbial mats. Subsequent lowering of the waters has caused the porous jarositic crusts to alter to potash alum ± akaganéite or schwertmannite. Meteoric water, with chloride concentrations of up to 10,000 µg/g, seeping through the roof produces a white, semi-thixotropic slurry which when dried yields 5.7 wt.% chloride and consisted of tamarugite plus halite. Some of this chloride (and sulfate) eventually enters the pool waters which have Cl− concentrations of 200 µg/g. This implies that the pools are not necessarily fed by a neutral pH alkali chloride fluid ascending from the geothermal reservoir, but are perched waters heated by ascending steam and fed largely by steam condensate.

The analytical characteristics of a W/Si multilayer dispersion element (MLDE) with a nominal 2d spacing of 60 Å are assessed and compared with those of a conventional thallium acid phthalate (TAP) crystal for the determination of fluorine in silicate and phosphate minerals by electron microprobe. Measured count rates for fluorine were found to be up to fourteen times higher using the MLDE compared with TAP giving improved detection limits of 0.02 to 0.08 wt. % F (six sigma, 100s count time) compared with equivalent data of 0.06 to 0.12 wt. % F by TAP. At equivalent spectrometer angles, peak widths by MLDE were broader by a factor of 2 to 3. However, an important advantage of MLDE was found to be the absence of multiple order diffractions higher than the second order. In consequence, the troublesome third order P-Kα line interference on the F-Kα line, normally encountered in the analysis of apatites, is absent in determinations made using the MLDE. Conversely small interferences on the F-Kα line were detected from the first-order Lα line of Fe and second-order Lα line of Mg. X-ray data and spectra of selected minerals are presented to demonstrate these interferences. Detection limits for elements that can also be determined using the MLDE were 0.07 to 0.15 wt. % oxygen and 0.34 wt. % carbon.

Antigorite is a lamellar variety of serpentine, and is supposed to be a dimorphous form of chrysotile, which is finely fibrous. Its chemical composition is approximately H4Mg3Si2O9, which is taken as the basis of calculations here.

This study was undertaken primarily because it was hoped that knowledge of the structure of antigorite would throw some light on that of chrysotile. Certain similarities between the two structures have been established, namely in the c(7·3kX or 14·6kX), and b(9·2kX) directions. There are two main differences, however. Firstly, imperfections which cause line broadening in the X-ray pattern of chrysotile, are absent in antigorite (apart from certain ‘streaks’). Secondly, the a(43·4kX) axis of antigorite is approximately eight times longer than the corresponding axis in chrysotile. A complete determination of the structure has not been achieved, but the X-ray pattern has been described, and some suggestions made as to the explanation of the peculiarities observed. A further study of the outstanding questions is in progress.

The crystal structure of averievite, Cu5O2(VO4)2·nMX has been determined. Trigonal system, space group P3, a = 6.375(1), c = 8.399(1) Å, V = 295.6(1) Å3, Z = 1, Dx = 4.01(1) g/cm3. The atomic arrangement is characterized by infinite nets parallel to (001) composed of [OCu4]6+ tetrahedra linked via corners in hexagonal rings. The bases of neigbouring tetrahedra are in one plane and their non-shared corners are turned to the opposite sides. The [VO4]3− tetrahedra are attached to the bases of [OCu4] tetrahedra. There are large (R >3.2 Å) channels in the structure where large molecular particles can enter. The comparison of the averievite structure with related compounds (in particular, copper oxovanadates) is given from the point of view of [OT4] polyion crystal chemistry.

Preliminary fluid inclusion measurements have been made on quartz (whole rocks and segregations) and garnet from a blueschist terrain. Although further measurements are required, the fluids apparently associated with the blueschist event are aqueous with no thermometrically detectable CO2, a feature which is consistent with mineral-fluid equilibria studies. The salinity of the fluid inclusions is highly variable, from almost pure H2O to halite saturation, and a mechanism involving hydration reactions, such as proposed by Crawford et al. (1979), is suggested. Fluid inclusions associated with the greenschist overprint, which has affected the terrain, are also aqueous in nature.

A sample of the zeolite paulingite from the locality Vinarická Hora was investigated by means of chemical, thermal, powder and single crystal X-ray methods. The fully transparent, colourless to pale yellow crystals exhibit the form {110} and occur together with phillipsite. The chemical composition is (Ca2.57K2.28Ba1.39Na0.38)(Al11.55Si30.59O84)·27H2O, Z = 16 with minor amounts of Mg (<0.05), Sr (<0.13), Mn (<0.01), and Fe (<0.04). The chemical differences from previously described paulingites are a high Ba-content, a lower Si/(Al+Fe) ratio of 2.64, and a reduced water-content. The calculated density is 2.098 g cm−3, and the observed refractive index is 1.482(2). The dehydration behaviour is characterized by a main weight loss from 24–190°C (−11.2 wt.%, ≅ 21H2O) and a minor weight loss from 190–390°C (−3.1 wt.%, ≅ 6H2O). The rehydration capability was proven up to 150°C. The dehydration process during the main weight loss is accompanied by a reduction of the cell volume of 11%. The refined lattice parameters of the X-ray powder data are a a = 35.1231 (5) Å and a = 33.7485(8) Å of an untreated and a dehydrated sample, respectively. A breakdown of the paulingite structure can be observed while the remaining water content decomposes. The single crystal X-ray refinement of this chemically different sample material derived three main cation positions, which are inside a so called paulingite or π-cage (Ca), between 8-rings of neighbouring π-cages (Ba), and in the centre of the non-planar 8-rings of the γ-cage (K). Further partially occupied cation positions (Ca,Na) were located in the planar 8-rings of the α- and γ-cages. No positions within the double 8-membered rings were detected. The water is localized around the main cation positions and in three clusters of partially occupied sites.