A Ca-poor rhodonite (CaO 1.31 wt.%), found in a quartz vein cutting manganese ore bodies, north of the Xanthi plutonic complex (northeastern Greece) was studied. Microprobe analyses with optical and physical properties are given. The cell dimensions, obtained by least squares calculation from direct θ value measurements on a Philips PW1100 single-crystal diffractometer are a = 7.626, b = 11.844, c = 6.702 Å, α = 92.44°, β = 94.28°, γ = 105.70°, V = 579.89 Å3, Z = 10, and space group P.

Effects of supercooling have been studied in a range of basaltic melts by isothermal and constant cooling rate experiments at one-atmosphere, using the wire-loop container method. The nucleation of plagioclase in these melts is systematically controlled by supercooling (-ΔT), time below the liquidus temperature, and initial superheating (+ΔT). The temperature at which the melt is initially superheated prior to supercooling controls the temperature at which crystal nucleation first takes place in a supercooled melt undergoing cooling; the greater the + ΔT the larger the degree of supercooling required prior to nucleation of the liquidus phase during cooling. In all six compositions investigated there are at least two fields in time-temperature space, one in which the liquidus phase always fails to nucleate on supercooling (favoured by small -ΔT) and one (favoured by large -ΔT) in which it always nucleates. These two fields may be separated by another in which the liquidus phase may or may not crystallize. Supercooling phenomena are not restricted to the liquidus phase but can also occur when the melt becomes saturated with subsequent phases. It is shown that the composition of plagioclase varies systematically with -ΔT and it is demonstrated that isothermal supercooling ‘lines’ can be used with a relatively high degree of accuracy to predict when nucleation of the liquidus phase will take place during constant cooling rate experiments.

Microscopic rods of wüstite and sulphide phases have been observed within silicate crystals from metallurgical slags. The rods, which are distinct from acicular crystals of accessory minerals, tend to be orientated perpendicular to the faces of the host crystal. These rods, and their constant orientation, are a product of the crystallization environment. It is proposed that they result from saturation of the melt with the relevant phase at the growth front of the silicate crystals. This microstructure is compared with known examples of microscopic rods and tubes in rocks.

The Caledonian fold belt of East Greenland contains calc-alkaline granite (sensu lato) intrusions with ages ranging from c.2000 Ma to c.350 Ma. The Proterozoic granites have low U contents and the pre-Devonian Caledonian granites contents of U corresponding to the clarke value for U in granites. Some aspects of the geochemistry of U are discussed using U-K/Rb, U-Sr, U-Zr, and U-Th diagrams. Secondary enrichment and mineralization occurs in fractured and hydrothermally altered granites and rhyolites situated in or near a major NNE fault zone. The U is associated with iron oxides or hydrocarbons. It is suggested that the source of the mineralization was Devonian acid magma, which also acted as a heat source for circulating hydrothermal fluids.

New chemical analyses of roeblingite from Franklin, New Jersey, and Långban, Sweden, are presented. The average composition of Franklin roeblingite is SiO2 24.9, CaO 23.8, SrO 2.4. MnO 2.4, PbO 30.2 SO3 10.4, H2O 6.13%, Sum = 100.23%. The data support space group C2/m and suggest the formula is (Ca,Sr)12 (Mn,Ca)2Pb4(SO4)4Si12O28(OH)20, if there is ordering on the site of rank 2.

The occurrence of three accessory minerals with significant rare earth contents in Tertiary acid rocks of St. Kilda is described. Allanite, zirkelite, and chevkinite were identified by electron probe analysis (with energy-dispersive attachment) and the chevkinite confirmed by X-ray diffraction. Brief comparison is made with other Tertiary occurrences of RE minerals. This is the first recorded occurrence of chevkinite in Great Britain.

The U content of cassiterite (SnO2), wolframite (Fe,Mn)WO4, and various sulphides from two localities in the Cornubian batholiths of south-west England has been investigated. Cassiterites showed concentrations of U between 0 and 6 ppm with the higher concentrations corresponding to the darker colour bands. Sulphides contained no detectable U using the fissiontrack method, but high concentrations relate to micro-veining. This veining was also evident in associated wolframite and appeared to have a composition similar to an iron-arsenate mineral associated with the alteration of arsenopyrite. Wolframite exhibited a wide range of U concentrations with sharp zonation and several generations of ore deposition within one crystal. The U was not, however, associated with either the iron- or manganese-rich phases.

The petrography and geochemistry of a suite of dolerite dykes emplaced into orthogneisses of the Jotun Nappe, central southern Norway, are described. The dolerites, which appear to be tholeiitic in character, show well-developed ophitic and doleritic textures and are not foliated. They contain corona structures of six types which represent the various stages of reaction between olivine or clinopyroxene and plagioclase, and oxide grains and plagioclase. Corona growth always proceeds after the plagioclase has become clouded with numerous extremely fine opaque particles, and reaches its fullest development in rocks with the most heavily clouded plagioclase. Garnet grows in coronas only in rocks with Fe2O3/(Fe2O3 + FeO) = 0.20 to 0.27. The ratio MgO/MgO + Fe2O3 + FeO) is of lesser importance in controlling the growth of this mineral. The role of water in coronaforming reactions, and the preservation of original igneous textures indicates that the coronas are a product of post-solidification deuterism, possibly active at high pressures and temperatures, rather than of prograde metamorphism.

The Bonser vein, one of the most productive sources of copper in the English Lake District, contains a mineral assemblage comprising quartz, chlorite, calcite, dolomite, stilpnomelane, magnetite, pyrrhotine, pyrite, marcasite, native bismuth, bismuthinite, laitakarite, joseite, arsenopyrite, chalcopyrite, sphalerite, galena, and cosalite. The phases pyrrhotine, sphalerite, arsenopyrite, laitakarite, joseite, and cosalite were analysed by electron microprobe. The occurrence of laitakarite is the first reported in the British Isles. Textures of the ore and gangue minerals show that the vein minerals were deposited successively in open voids. The sequence of deposition was of quartz forming throughout, early chlorite and stilpnomelane with some dolomite and calcite, magnetite as the earliest opaque phase, followed by arsenopyrite, pyrrhotine, sphalerite, chalcopyrite, pyrite, and marcasite; the bismuth- and lead-bearing minerals were the last to form.

The data on the coexisting phases and their compositions have been used to estimate the temperatures of mineralization and the activities of sulphur and oxygen. Magnetite and arsenopyrite appear to have formed at 350–400% with aS2 reaching 10−12 to 10−14 atm. and aO2 around 10−24 to 10−29 atm. The assemblage of quartz, chlorite, stilpnomelane, calcite, dolomite, pyrrhoine, chalcopyrite, sphalerite, and (late) arsenopyrite was probably deposited at ∼ 240°C, with aS2 decreasing to 10−15 to 10−16 atm and aO2 to 10−38) to 10{su−44 atm. The later minerals probably formed at temperatures as low as 200°C and under similar conditions of sulphur and oxygen activity.

Found by N. Theis at a uranium prospect near Durango, Colorado. Occurs with uraninite, galena, malachite, azurite, etc. Colour pale blue-green, H = 1½, G = 4.25. Optically 2Vα ≈ 0°, α = 1.755, β = γ = 1.785; non-pleochroic. Chemical analysis on 1034 µg gave CuO 33.3 %, ZnO 33.1, CaO 0.3, As2O5 14.8, Sb2O5 7.0, H2O 10.5 leading to Cu5Zn5{(As,Sb)O4}2(OH)14. The cell indexes as orthorhombic a = 8.225Å, b = 7.123, c = 14.97. Strongest lines are 14.97 (9), 7.483 (5), 4.112 (4), 3.741 (10), 2.996 (4), 2.534 (9), 1.830 (5), 1.553 (3). The mineral and name have been approved by the Commission on New Minerals and Mineral Names, IMA.

A new sodium aluminium sulphate phosphate has been named peisleyite. It has the ideal formula Na3Al16(SO4)2(PO4)10(OH)17 · 20H2O. It occurs as fine-grained, compact, brittle, white material on dumps at Tom's Phosphate Quarry, near Kapunda, South Australia. Strongest X-ray diffraction lines are 12.63 Å (100) 010, 7.82(35) 11, 5.41(35) 004, 7.59(30) 111. Unit cell parameters are a 13.31 ± 0.006, b 12.62 ± 0.006, c 23.15 ± 0.01 Å, β 110.0°±0.03°, Z = 2.

U-enriched granites occur in a Precambrian window in the Caledonides of central Sweden and intrude an extensive supracrustal formation dominated by acid terrestrial volcanics. During the Caledonian orogeny, thrusting, foliation, mylonites, and mesoscopic folds developed in the Precambrian rocks under low-grade metamorphic conditions. Ground and airborne γ-spectrometry indicate U-enrichment mainly in the northern part of the window where two uraniferous granites have been intruded. Several small U vein-type mineralizations are associated with one of the granites. The largest occurrence of the mineralization might be economic, and a Rb-Sr age determination has established a minimum age of 1500 Ma on the associated granite which is highly evolved.

Euhedral crystals of the low-temperature mineral lansfordite, MgCO3 · 5H2O, have been prepared from saturated magnesium bicarbonate solutions at temperatures below 10°C. The crystals are monoclinic P21/a with a = 12.4758(7), b = 7.6258(4), c = 7.3463(6)Å, β = 101.762(6)°, V = 684.24Å3, Dcalc. = 1.693 g cm−3, Dobs. = 1.70(1) g m−3. At room temperature, the crystals slowly effloresce to produce pseudomorphs of nesquehonite, MgCO3 · 3H2O. Dehydration is complete at 300°C, with decarbonation taking place in the interval to 560°C. A new X-ray powder diffraction pattern is presented, and details of the infra-red absorption spectrum are discussed.

Dwornikite, (Ni1−xFex)SO4 · H2O is a member of the kieserite group, monoclinic with space group C2/c. Specimens from Minasragra, Peru with x ∼ 0.1 have a unit cell with a = 6.839(2), b = 7.582(2), c = 7.474(2) Å, and β = 117.85(2)°. The six strongest lines of the powder pattern are: 3.342 (12, 100), 4.732 (110, 70), 3.024 (200, 70), 4.754 (11, 50), 3.293 (021, 35), 2.491 (022, 35). The mineral occurs as fine grained white aggregates associated with vanadium sulphide ores containing patronite and bravoite, mixed with other oxidation products. New unit cell data for the synthetic end-member compounds NiSO4 · H2O and FeSO4 · H2O, and new X-ray powder data for retgersite (NiSO4 · 6H2O) are provided.

U and Th data have been obtained by γ-ray spectrometry on samples from thirty quarry sites in the Elberton batholith, a large (500 km2) late orogenic (320 Ma) mesozonal biotite granite in the Southern Piedmont, USA. The granite is enriched in the Th (=42ppm), but U contents (=3ppm) are close to the average abundance for granites (18 ppm Th; 4 ppm U). Th/U ratios vary widely throughout the batholith, ranging from 3 to 58, with an unusually high mean of 18±10 (1). At some localities, lower Th/U ratios, high U contents of zircons (1500 ppm), and similarities to two-mica granites which have low Th/U ratios of ∼ 1 indicate that the granite once had a much higher U content. Pegmatites are enriched in U (up to a factor of 8), but Th contents are low (by a factor of 3) compared with the granite suggesting loss of U from the granite by an early magmatic vapour-phase. Significant U loss may also have occurred as a result of groundwater leaching, possibly associated with uplift and weathering of the intrusion 200 Ma ago. The highest Th/U values occur in the upper portions of the batholith, consistent with the hypothesis of U loss by these processes. The U content is highly variable throughout the batholith but Th is more uniform, both regionally and at outcrop. The distribution of Th does not correlate with patterns shown using previously published, 18O/16O, 87Sr/86Sr, or trace element (Ba, Rb. Sr, Mn) data, which are thought to reflect inhomogeneity in the protolith of the granite although the possibility that at least some of the isotopic ratios were disturbed by late alteration processes cannot be eliminated.

Found on a specimen in the mineral collection of the National Museum of Wales, no. NMW 27.111.GR414, from the Aberllyn mine, Llanrwst mining field, North Wales, with hydrozincite on a breccia cemented by sphalerite, quartz, calcite, and ankerite. Atomic absorption and TGA analyses gave ZnO 37.8, CuO 22.0, SO3 14.9, H2O 24.5, total 99.2%, corresponding to (Zn2.50 Cu1.49)Σ3.99 S1.00 O7·7.32 H2O on the basis of total O = 7 in the anhydrous part. The ideal formula is (Zn,Cu)4SO4(OH)6·4H2O where Zn > Cu. It is hexagonal a 8.29, c 10.50 ± 0.01 Å, possible space groups P6, P, P6/m, P622, P6mm, Pm2, P2m, and P6/mmm. Isomorphous with synthetic Zn,SO4(OH)66·4H2O and (Zn,Cu)4SO4(OH)6·4H2O. Strongest X-ray powder diffractions are: 10.59(100)0001, 5.31(15)0002, 4.15(25)110, 2.71(42)210, 2.63(41)211,0004, 2.41(22)212, 1.57(23)322, 1.55(20)411. Namuwite is pale sea-green in colour, lustre pearly, streak very pale green, H (Mohs) 2. Cleavage {0001}, perfect. Density (g/cm3) 2.77 (meas.), 2.81 (calc. on the normalized empirical formula). It is optically uniaxial, sign not determined owing to the extremely low birefringence. Refractive index n = 1.577(5)(NaD). The mineral and name have been approved by the Commission on New Minerals and Mineral Names, IMA.

Scourian ultramafic granulites from the Assynt region, of Sutherland were retrogressed to amphibolite facies during the Inverian and in Laxfordian shear zones. Inverian assemblages are dominantly chlorite and tremolite with minor anthophyllite and dolomite. Laxfordian assemblages are cummingtonite, chlorite, and dolomite with only minor amounts of tremolite. Retrogression took place on a falling temperature path with temperatures between 750 and 550°C, and with H2O forming more than 90% of the fluid phase. Initially retrogression was caused by the influx of large volumes of hydrous fluid associated with the development of Inverian folds. During the Laxfordian shearing PCO2 was increased slightly. Serpentinization of olivine occurred at a much later stage.

Uraniferous granites occur in several different geological settings in the Swedish Precambrian and represent a variety of granite types and ages. Granites with > 10 ppm U are highly differentiated leucocratic alkali granites with initial 87Sr/86Sr ratios over 0.708. They commonly show enrichment in F, Sn, W, and/or Mo, while mineralization of these dements may, in some cases, be found in the nearby country rock. Radiogenic heat from the granites may have assisted hydrothermal circulation. In only one case, Hotagen, is important U mineralization thought to be directly related to a U-rich granite, while the majority of epigenetic U mineralizations with economic potential are related to hydrothermal processes in areas where the bedrock is regionally enhanced in U.

X-ray powder methods have been used to study the room-temperature structures of the synthetic sodalites: Li8(Al6Si6O24)Cl2, K7.6Na0.4(Al6Si6O24)Cl2, and Na8(Al6Si6O24)I2. Natural sodalite was also studied and the atomic coordinates show satisfactory agreement with those determined from the single-crystal data of Löns and Schulz (1967). The LiCl- and KCl- as well as the NaCl-sodalites refined in the expected sodalite space group P3n, but the NaI-sodalite fitted 13m better. The resulting structural data reveal shortcomings in the previous computer models for sodalite structures and an improved computer modelling procedure is devised which successfully predicts atomic coordinates, starting from the experimental a value and an estimate of the cationanion distance. The method incorporates the experimental result that the average T-O distance (T = Al, Si) throughout the samples is ∼ 1.678 Å, and Si-O and Al-O are set at 1.618 and 1.738 Å, respectively. Although T-O remains little changed throughout the samples, the data confirm the inverse relationship between ∠ T-O-T and the tetrahedron tilt angle ϕ, in which ∠ T-O-T approaches ∼ 160° as ϕ → 0° and the sodalite cage becomes fully expanded.

The first occurrence of new mineral ardaite (a chlorine sulphosalt) has been discovered in the Madjarovo polymetallic ore deposit (Bulgaria). The average composition is Pb 56.50, Ag 0.04, Sb 22.48, S 15.56, Cl 3.78, total 98.36 wt.%. The formula is Pb20–18 Sb12–24S34–36.5Cl6–8. The mineral occurs as fine acicular aggregates associated with galena, nadorite, a Cl-bearing robinsonite and Cl-beating semseyite, pyrostilpnite, silver- bearing tetrahedrite and anglesite.