Ferrocarpholite has been discovered at two localities in low-grade blueschists in the Diahot region, northern New Caledonia. In one occurrence (specimen 23503), ferrocarpholite was found in quartz veins associated with metamorphosed rhyolitic tufts, and at the other locality (23514) it occurs as a gangue mineral at Ao Mine associated with quartz, a variety of carbonates, and sulphide ores.

The Dippin sill, which is emplaced into the Triassic sediments of SE Arran, is an alkaline basic sheet which displays pronounced hydrothermal alteration. The 40-m-thick sill has suffered pervasive contamination with radiogenic Sr, introduced from the Triassic sediments by hydrothermal fluids. Stable isotope measurements suggest that fluids were of meteoric origin, but were restricted to a small closed-system circulation. Initial 87Sr/86Sr ratios in the sill were raised from an original value of 0.7032 to a maximum of 0.7091, contamination being especially pronounced near the contacts at Dippin Head itself (localities 12 and 14) and in a drill core section through the sill above Dippin. Hydrothermal Sr was incorporated into an early-formed high-CaO, high-Sr analcime, which replaced unstable high-silica nepheline in interstitial patches. However, this high-CaO analcime, along with plagioclase, was later replaced by a low-CaO, low-Sr analcime, allowing Sr leaching from the margins of the sill. Hydrothermal fluids are thought to have migrated up to 1 km laterally, up the dip of the sill, mainly via tension joints forming in the cooling intrusion. Pooling of hot fluids at the upper end of the sill probably raised water/rock ratios in this region and allowed greater Sr contamination during mineralogical alteration. The undersaturated mineralogy of the sill accounts for its pervasive hydrothermal Sr contamination, which contrasts markedly with the relatively undisturbed Sr isotope compositions of Hebridean granites involved in hydrothermal systems.

Cordierite commonly alters to chlorite-sericite, called pinite. Besides pinite alteration, cordierite from the Fishtail Lake shows textural evidence indicating retrogression to kyanite, andalusite, and coarse flakes of chlorite. This is consistent with the experimental data on the stability of cordierite and may be expected to be limited to potash-deficient rocks, such as the cordierite-garnetgedrite bearing gneisses of the area. In common potash-bearing pelitic rocks, retrogression of cordierite results in the formation of sericite and chlorite. In gneisses containing sillimanite and cordierite, the breakdown of cordierite in this way results in the association of the three aluminosilicates (kyanite, andalusite, and sillimanite) in the same rock. The association of kyanite-andalusite in equilibrium probably suggests that the retrogression of cordierite took place close to the univariant line of kyanite-andalusite.

New chemical analyses, electron and X-ray powder diffraction data, and comparison with gyrolite and reyerite show that tungusite has the ideal formula , symmetry P and a = 9.714(9), b = 9.721(9), c = 22.09(3), α = 90.13(1)°, β = 98.3(2)°, γ = 120.0(1)°, Z = 1. A structural model for tungusite is derived by splitting the double tetrahedral layer of reyerite and inserting a trioctahedral X sheet which is ideally occupied by Fe2+. Polytypism phenomena due to different relative positions between tetrahedral and X sheets are discussed. A substitutional solid solution represented by the formula [Ca14(OH)8]Si24−yAlyO60[NaxM9−(x+z)□z(OH)14−(x+y+2z)·(x+y+2z)H2O] includes tungusite (x = y = z = 0, M = Fe2+ and gyrolite (x = 1, y = 1, z = 6, M = Ca).

The crystal structure of tedhadleyite, ideally Hg2+Hg101+O4l2(Cl,Br)2,triclinic, AĪ, a 7.0147(5), b 11.8508(7), c 12.5985(8) Å, α 115.583(5), β 82.575(2), γ 100.619(2)º, V 927.0(2) Å3, Z = 2,was solved by direct methods and refined to an R1 index of 4.5% for 2677 unique reflections. There are six symmetrically distinct Hg sites in tedhadleyite: Hg(1) is occupied by Hg2+ and Hg(2–6) are occupied by Hg+ that forms three [Hg–Hg]2+ dimers with Hg–Hg separations between 2.527 and 2.556 Å. These [Hg–Hg]2+ dimers have strong covalent bonds to O atoms,forming pseudo-linear O–Hg–Hg–O arrangements,and weak bonds to halogen and O atoms at high angles to the dimer axis. The [O–Hg–Hg-O] groups share anions to form four-membered square rings of composition [Hg8O4] that link along [100] via [O–Hg–Hg-O] groups and along [001] via [O–Hg–O] groups, forming rectangular rings of composition [Hg14O8]. The rings form a corrugated layer that interweaves with a symmetrically related layer whereby the [O–Hg(6)–Hg(6)–O] linking groups of one layer pass through the centres of the square [Hg8O4] rings of the other layer to form [Hg11O4] complex slabs parallel to (010) that link through Hg-I and Hg-Br,Cl bonds.

The crystal structure of a Te-rich polybasite has been refined by means of X-ray diffraction data collected at room temperature (space group Pm1; R = 0.0505 for 964 observed reflections and 94 parameters; refined formula Ag14.46Cu1.54Sb1.58As0.42S9.67Te1.33). The structure comprises stacking of [(Ag, Cu)6(Sb, As)2(S, Te)7]2–A and [Ag9Cu(S, Te)2(S, Te)2]2+B layer modules in which Sb forms isolated SbS3 pyramids, as occurs typically in sulfosalts, Cu links two S atoms in a linear coordination and Ag occupies sites with coordination ranging from quasi linear to almost tetrahedral. The silver d10 ions are found in the B layer module along two-dimensional diffusion paths and their electron densities evidenced by means of a combination of a Gram-Charlier development of the atomic displacement factors and a split model. The Te-for-S substitution occurs at the same structural sites that Se substitutes for S in selenopolybasite and the Te occupancy at one of these sites is 0.49, thus suggesting the possibility that 'telluropolybasite' could be found in nature.

Quartz-gahnite-sillimanite asssemblages are described from a supracrustal enclave at Kraaifontein, 45 km south-west of Springbok in the Namaqualand Metamorphic Complex, South Africa. The assemblage formed by prograde reaction in the granulite facies zone during the 1100 Ma Namaqua event, possibly as the result of desulphidation of sphalerite. Subsequent lower-amphibolite-facies retrogression occurred in close proximity to shear zones during an early Pan-African metamorphic event at 700 Ma. Zincian staurolite formed as overgrowths on gahnite in a hydration reaction involving the consumption of gahnite, quartz, and sillimanite. Compositional zoning to more zinc-rich rims in gahnite at Kraaifontein is unrelated to the retrograde reaction, but is interpreted as a result of changing conditions during the prograde Namaqua event.

A detailed understanding of the response of mineral phases to the radiation fields experienced in a geological disposal facility (GDF) is currently poorly constrained. Prolongued ion irradiation has the potential to affect both the physical integrity and oxidation state of materials and therefore may alter a structure's ability to react with radionuclides. Radiohalos (spheres of radiation damage in minerals surrounding radioactive (α-emitting) inclusions) provide useful analogues for studying long term α-particle damage accumulation. In this study, silicate minerals adjacent to Th- and U-rich monazite and zircon were probed for redox changes and long/short range disorder using microfocus X-ray absorption spectroscopy (XAS) and high resolution X-ray diffraction (XRD) at Beamline I18, Diamond Light Source. Fe3+ → Fe2+ reduction has been demonstrated in an amphibole sample containing structural OH– groups – a trend not observed in anhydrous phases such as garnet. Coincident with the findings of Pattrick et al. (2013), the radiolytic breakdown of OH– groups is postulated to liberate Fe3+ reducing electrons. Across all samples, high point defect densities and minor lattice aberrations are apparent adjacent to the radioactive inclusion, demonstrated by micro-XRD.

Nickelblödite, the nickel analogue of blödite, has been discovered in nickel mines at Kambalda and Carr Boyd Rocks in Western Australia. The Kambalda sample, found in an underground opening, has a composition corresponding to Na2·02(Ni0·79Mg0·14Fc0·05)(SO4)2·00·3·17H2O. The sample from Carr Boyd Rocks, collected from an open pit, is a more magnesian variety, with a composition corresponding to Na1·93 (Ni0·55Mg0·46Cu0·02Co0·02)(SO4)2·01·4·39H2O. The mineral occurs as a surface efflorescence on nickel-rich sulphide ore in both cases. Nickelblödite is light green and transparent, and occurs as tabular crystallites up to 150 μm in diameter. The Kambalda material is biaxially negative with 2V = 60–70° α = 1·513, β(calc) = 1·518 and γ = 1·520. D 2·43, indentation hardness VHN 139. The Carr Boyd material has lower refractive indices and hardness. Strongest lines of the indexed powder pattern (Kambalda sample) are 4·466(9), 4·193(7), 3·720(6), 3·223(10), 3·190(8), 2·589(6). These measurements conform to a monoclinic unit cell with α = 10·87, b = 8·07, c = 5·46Å, and β = 100·72°. The possibility of H3O+ substitution is discussed.

The present work analyses the thermal behaviour of alum-(K), KAl(SO4)2·12H2O, by in situ laboratory high-temperature powder X-ray diffraction data from 303 K to melting, which starts at 355 K and is completed, due to kinetics, at 359 K. The calculated a0 linear thermal expansion coefficient is of 14.68(11) × 10–6 K–1 within the investigated thermal range. The k disorder parameter, describing the extension of the orientational disorder of the sulfate group, has been found to decrease from ∼0.70 to ∼0.65 just before melting. It has been demonstrated that the occurrence of the disorder implies the coexistence of K+ ions in both six- and seven-fold coordination. This is necessary for assigning a reasonable bond-valence sum of 0.81 valence units (vu) to the 'average' K+ ion a instead of 0.66 vu, which is obtained in the case of six-fold coordination alone. We can describe the temperature dependence of k from 93–355 K by means of the empirical equation k = 0.798(12) + 2.5(11) × 10–4 T – 1.9(2) × 10–6T2, which includes reference low-temperature data. Bond-valence analysis has shown that, on cooling, an increase of the k disorder parameter and shortening of the K–O2 bond distance act together to maintain constancy in the bond-valence sum at the K site, stabilizing the structure. Therefore, the need for keeping the 'average' K+ ion at a reasonable bond-valence sum appears to be the driving force for the ordering process involving the sulfate group.

Veins in the Central Aar granite consisting of zoisite, plagioclase, albite, alkali feldspar, muscovite, tremolite, quartz, and calcite are described. The zoisite is a thulite with up to 0.20 wt% MnO. It is argued that the zoisite is derived from granite plagioclases and has recrystallized in veins during alpine greenschist metamorphism. By later increasing XCO2 or decreasing temperature zoisite decomposed to calcite, plagioclase, and muscovite.

Thulites from different localities were investigated by X-ray and by electron microprobe analysis. Both orthorhombic and monoclinic members of the epidote group having low MnO contents have been described as thulites. It is suggested that low MnO values in the range 0.05 to 0.9 wt% cause the pink colour of thulites, regardless of symmetry.

Found at a small prospect in the Artillery Peaks area, Arizona. Luddcnite occurs in oxidized Cu-Zn ores with fluorite, alamosite, and cerussite. Colour nickel green, H = 4, G meas. 4.45.

Strongest X-ray lines are 7.361(10), 3.173(10), 2.918(8), 5.218(7), 4.226(5), 3.411(5), 2.888(5), 3.650(4). A possible cell found by Ito method is a = 7.85, b = 20.06, c = 14.72 Å, β = 90.78° (monoclinic). Optically (+), α = 1.852, γ = 1.867.

Chemical analysis by wet methods gave CuO 13.2%, PbO 35.1, SiO2 25.7, H2O 20.5, TiO2 (leucoxene impurity) 4.7. Not all water need be essential, hence Cu2Pb2Si5 O14·nH2O. The new mineral and name have been approved in advance of publication by the Commission on New Minerals and New Mineral Names, IMA.

Arsenic-rich nagyagite (up to 5.5 wt % As) has been discovered in samples from the Au-Ag-Te deposit of Sacarimb, western Romania. Optical properties of the mineral show small but distinct differences to nagyagite (ss). Chemical analyses indicate a substitution of As for Sb, and chemical zonation suggests rapid changes in the chemistry of the mineralising fluids.

In southern Kerala, India, chrysoberyl occurs in granitic pegmatites in association with quartz in alkali feldspar and is thought to crystallize earlier than beryl and sillimanite. The pegmatites are thought to have derived from the residual melts of granitic liquids formed by partial melting of the khondalites. In the absence of pyrometasomatic, desilication or aluminium-contamination processes, the genesis of chrysoberyl is explained by the CO2 activity in residual melts. This model is at variance with the known concepts and may also explain the genesis of chrysoberyl in Sri Lanka where it is still controversial.

Willemite is a mineral of comparatively rare occurrence, but it has long been mined in New Jersey as an important, ore of zinc (Zn2Sio4, containing Zn 58.6 %), and it would seem also to be abundant in Rhodesia. In the standard mineralogies of Dana (1892) and Hintze (1889) it is mentioned from only four districts. As there is some confusion in the statement of these few localities, and further as several others have been discovered during recent years, a complete list of localities for this mineral has been compiled from the literature; and some others represented by specimens in the British Museum collection are added, inchding the African occurrences now to be described.

The hypersthene-gabbro of Ardnamurchan Point is the earliest of the intrusions of Centre 2 of the Ardnamurchan complex as shown by 5. E. Richey (11, p. 208).I The mass is intruded into domed Jurassic sediments and Tertiary basalt flows (fig. 1). The main part of the intrusion is composed of rather fine-grained gabbro, containing 2-3 % of hypersthene which typically surrounds crystals of olivine. Marginally, however, the gabbro is a quartz-bearing variety, with a micrographic mesostasis. The outer contact is somewhat sinuous due to the fact that the intrusion has only been exposed to a comparatively small depth below its original roof. This same geological accident may account in part for the number of fine-grained, basic, granular masses that are locally abundant within the gabbro.

Although the mineral spinel belongs to an isomorphous group, and in the simple formula MgO.Al2O3 a both Mg and A1 are susceptible to isomorphous replacement, yet in the transparent varieties oI gem quality there is, as a rule, very little deviation from the type composition, and the physical properties are moderately constant. In fact, one may say that the only considerable replacement hitherto recorded in spinels used as gemstones is by ferrous iron in the variety known as ceylonite or pleonaste, which is black and opaque even when 7 or 8 % of FeO is present, the end-member of this series being hercynite, FeO.Al2O3, with 41% ferrous oxide.

The purpose of this paper is to draw attention to certain transparent blue spinels from the gem gravels of Ceylon, the physical properties of which differ quite strikingly from those of the normal spinels, from which they are indistinguishable in appearance, magnesium being replaced in this instance not by ferrous iron but by zinc.

Barringtonite, a new hydrous magnesium carbonate of composition MgCO3,2H2O, is recorded from Sempill Creek, Barrington Tops, New South Wales, where it occurs as nodular encrustations on the surface of olivine basalt. The mineral is triclinic, biaxial positive, has refractive indices α = 1·458, β = 1·473, γ = 1·501, 2Vγ = 73° 44′, and using Ito's method (1949) cell dimensions α = 9·155 Å, b = 6·202 Å, c = 6·092Å, α = 94· 00′, β = 95· 32′, and γ = 108° 72′. The three strongest lines on an X-ray powder photograph give d values of 8·682, 3·093, and 2·936 Å.