Ruizite is a new mineral found in the mesogene calc-silicate assemblage at the Christmas mine, Gila County, Arizona. Occurs with kinoite, apophyllite, smectite, and junitoite. Colour is orange inclining to brown with pale streak, H = 5, Sp. Gr. meas. = 2·9. Crystals monoclinic 2/m, elongate on [010]; a = 11·95 Å, b = 6·17, c = 9·03, β = 91° 22½′. Probable space group P21/c with Z = 4 giving Dcalc = 2·997. Strongest lines are 11·951 Å(10), 4·190 (7), 3·116 (6), 5·092 (5), 3·644 (4), 2·951 (4), 2·591 (4), 2·132 (4). Indices are α = 1·663, β = 1·715 ‖ [010], γ = 1·734, 44° to [001] in obtuse β; 2Vα = 60·2°; inclined dispersion p > v strong. Twinned on {100}. Analysis by wet methods gave CaO = 20·57%, Mn2O3 = 23·42, SiO2 = 39·14, H2O = 16·0 leading to or CaMn3+ (SiO3)2(OH). 2H2O.

Named for its discoverer, Joe Ana Ruiz of Mammoth, Arizona

Claringbullite, Cu4CI(OH)7.nH2O where n is about 0·5, a new mineral, is reported as soft blue plates in cuprite from Nchanga open pit, Zambia and Kambowe, Mina M'sesa, Katanga. The mineral is hexagonal a 6-6708, c 9·183 Å, Z = 2. Optically, claringbullite is uniaxial negative with ω = 1·782 and ε = 1·780. Indexed powder data are given together with five electron-probe analyses of the mineral.

A new calcium aluminum silico-phosphate mineral has been found at two locations on Newry Hill, Newry, Maine, U.S.A. Its composition closely approximates to 3CaO.3·5Al2O3.3SiO2.2P2O5.18H2O (Z = 1). Perhamite is uniaxial (+), c = 1577, ω = 1·564, density = 2·64 g/cm3. The mineral is hexagonal, probably P6/mmm, with a = 7·02 Å, c = 20·21 Å. The colour is light brown to white, the habit is as aggregates of discoidal hexagonal crystals. Cleavage is perfect {0001}, the lustre is vitreous, and the streak white. The mineral is named for a pegmatite miner and geologist, Frank C. Perham of West Paris, Maine, U.S.A.

The most similar species is viséite. A re-examination of viséite indicates that the composition previously given is incorrect. A new form of viséite, also from Visé, Liège, Belgium is also examined and found to differ in composition from the type material.

Kerolites from Goles Mountain (Yugoslavia), Wiry (Poland), Madison Co. (North Carolina), and Kremze (Czechoslovakia) are compared with talc and stevensite. Chemical analyses give a composition for kerolite near R3Si4O10(OH)2.nH2O with R mainly Mg and n about 0·8–1·2. Infra-red data and dehydration-rehydration experiments suggest that the additional water is partly surface-held hydrogen-bonded molecular water, lost up to about 300 °C and easily recoverable, and ‘water’ held as surface hydroxyls, lost at temperatures up to about 650 °C and less easily recoverable. The surface area of kerolite from North Carolina by nitrogen absorption measurements is 196 m2/g.

X-ray data show broad basal reflections, a basal spacing (after Lorentz-polarization correction) of about 9·6 Å and a crystallite size of about five structural layers, which is consistent with the large surface area. Two-dimensional hk bands indicate a randomly stacked layer structure with b ≈ 9·14 Å and a crystallite ‘diameter’ of about 150 Å. The basal spacing shows no expansion in water and no thermal contraction up to 500°C. A partial and irregular swelling with ethylene glycol is obtained only after prolonged cxposure (several weeks). In both respects, kerolites differ from stevensite. Kerolites come close to talc in structure and composition but differ in having a highly random layer arrangement, a slightly enlarged basal spacing, which could be due to misfit of layers caused by random stacking, and weaker interlayer bonding.

Kerolite is considered to be a useful varietal name for this talc-like mineral in agreement with the views of D'yakonov and of Maksimovic. It cannot be defined as serpentine + stevensite.

The decomposition of chrysotile fibres heated in air has been studied in the range 100–1400°C by electron microscopy and infra-red absorption. The first observable change in the structure occurred at 580°C, where cavities started to open up between the (001) layers of chrysotile as the fibres were dehydrated, giving rise to strong low-angle diffraction. There was no evidence of any structure in the remaining material but some degree of the original atomic arrangement was preserved for the magnesium silicates, forsterite, and enstatite, later developed in certain preferred orientations. The manner of this crystallization was determined by the thermal treatment, for in samples held between 600°C and 800°C forsterite developed slowly with little further disruption of the fibre while above 800°C the remaining amorphous areas rapidly recrystallized to a mixture of forsterite and enstatite. It is suggested that the mechanisms described by other investigators to explain the development of forsterite in preferred orientations may serve simply to nucleate the crystallization and a similar mechanism to account for the nucleation of the enstatite crystallization is considered. At high temperatures a possible doubling of some of the lattice parameters of the silicates was observed.

After approximately 50% of K from the 1–2 μm fraction of a naturally occurring microcrystalline muscovite was extracted with BaCl2 solution at 98°C electron-diffraction patterns showed a honeycomb-shaped diffuse scattering as well as intense diffuse streaks. The diffuse scattering became pronounced with increasing K-depletion. It may be interpreted in terms of a short-range order distribution of interlayer Ba ions, using an analogy to the work by Alcover et al. (1972, 1976). Since the diffuse streaks still remained after re-entry of K to the K-depleted specimen they might be related to structural disturbance, particularly in the basal oxygen arrangements, resulting from the K-extraction. Subsequent conversions of Ba-saturated vermiculitized muscovite into Na-, Mg-, and Ca-forms revealed distinct extra diffraction spots midway between two ordinary diffraction spots. They were broader than the ordinary spots and elongated along the three directions of [01]*, [11]*, and [11]*. The diffraction pattern containing the extra spots was, therefore, interpreted as a composite one made up by superimposing three independent patterns, each of which was composed of ordinary Bragg diffraction spots and extra diffraction maxima elongated in one of the three directions. This situation does not require a superlattice but modified the original face-centred lattice symmetry to a primitive lattice symmetry. However, the presence of a real superlattice should also be possible. The elongation and broadness of the extra diffraction maxima may be related to the orientation and size of coherent domains defined by a certain ordering of interlayer cationic distribution, which took place during the hydration processes including extraction and conversion.

Compositions of An61 and An69·5 have been determined for two domains in plagioclase from a gneiss. Optical properties indicate that the same compositions apply respectively for an intergrowth of ‘matrix’ and lamellae found in zones between the domains. The intergrowth appears to span the composition range between the Bøggild and Huttenlocher intergrowths.

Unusual replacement-type sulphide mineralization occurs in the northern part of the Bulong Complex, about 30 km east of Kalgoorlie, Western Australia. The mineralization is non-economic (up to 0·5% Ni, 0·4% Cu, 0·1% Co, and 8·6% S) and occurs in altered unlayered olivine-rich rocks immediately above a thin sheet-like inclusion of country rock. The supergene-modified primary opaque assemblage pyrrhotine-magnetite-pyrite-chalcopyrite-(pentlandite) is texturally unusual in that the opaques are largely pseudomorphic after primary olivine grains, mainly within irregular fracture networks in a manner similar to ‘early’ serpentine. Textural relations between opaques and silicates indicate that the mineralization was introduced during the early stages of serpentinization prior to the onset of deformation and regional metamorphism. Monoclinic pyrrhotine is the main opaque phase, with some grains containing relict cores of the hexagonal variety. Magnetite associated with the mineralization is Ni-poor (< 0·1% Ni) compared with ‘serpentinization magnetite’ from elsewhere in the Bulong Complex, which contains 0·5–0·8% Ni. As the mineralization was intersected at relatively shallow depth, supergene alteration effects are evident; pyrrhotine is locally altered to pyrite and marcasite (texturally and chemically distinct from the primary pyrite), and pentlandite is largely replaced by cupriferous violarite.

Textural features and consideration of phase relations in the system Cu-Fe-S-O suggest that the mineralization is of low-temperature (350± °C) hydrothermal origin. By contrast, the more commonly developed Fe-Ni-Cu sulphide mineralization of the Kalgoorlie region is generally considered to be of high-temperature (1200± °C) magmatic origin.

Spherulitic and felted green to brown minerals are described from various volcanic rocks of the Western Ochils, Stirlingshire. They fill amygdales and replace pyroxenes and appear to be an interlayered series of sheet silicates from celadonite to vermiculite. The minerals are hydrothermal in origin and suggest the presence of a potassium-rich hydrous fluid at a late stage in the volcanic history.

Mayo Belwa, a highly shocked enstatite achondrite, fell during the evening of 3 August 1974 in the Adamawa District, NE. Nigeria (8° 58' N., 12° 05' E.). The stone weighed 4·85 kg and was deposited in the Geological Survey of Nigeria and loaned for study to the British Museum (Natural History). It is composed principally of enstatite (0·02 FeO%), with some olivine (Fo100), diopside, feldspar (An9 Ab88 Or3), and minor Fe-Ni metal and the sulphides oldhamite, daubréelite, ferroan alabandine, and troilite. The kamacite contains between 0·15% and 1·2% Si and the troilite contains 1·1% Ti. The meteorite possesses vuggy cavities, which contain fluor-amphibole needles projecting from their walls, suggesting the presence at some time of a volatile-rich phase. The titanium-rich troilite, the nearly ironfree enstatite and the Mg/Si ratio are typical of the E-achondrites.

Fassaitic diopside containing 22–23 wt% Al2O3 (approximately 41–43% calcium Tschermak's molecule, CaAl2SiO6) and melilite containing 69–43% gehlenite crystallized from a blast-furnace slag at atmospheric pressure between about 1450°C and 1250°C. The occurrence is of petrological interest because the association of pyroxene with gehlenite-rich melilite has not been recorded from experimental studies in the system CaO-MgO-Al2O3-SiO2, and because of the similarity of the compositions of both minerals to pyroxene and melilite in the Ca-Al-rich inclusions of the Allende meteorite.

The stratigraphical limits on the age of the Freetown intrusion, Sierra Leone, are very wide, yet the intrusion has not previously been accurately dated by isotopic methods, despite a number of attempts. Rubidium-strontium dating of acid veins contemporaneous with the early stages of the prolonged cooling history of the intrusion provides an age of 193 ± 3 Ma. The veins consist of quartz and orthoclase with relict minerals, principally plagioclase, from thehost gabbro. Electron-microprobe analysis of the altered minerals of the veins, and the petrography of the vein and adjacent host gabbro clearly demonstrate that the veins were formed from a granitic fraction, differentiated in situ from the surrounding solid gabbro with the assistance of a hydrous fluid phase within the incipient vein. This assertion is supported by the identical, low value of the initial 87Sr/86Sr ratio (0·70389) obtained from both the acid and basic rocks, and the technique described here may be useful in dating other, similar, intrusions.

Petrography of an original websterite from Jotunheimen shows evidence of plagioclase exsolving from clinopyroxene to form both internal lamellae and also an intergranular symplectite with olivine and magnetite hercynite. The olivine is secondary, forming from both clinopyroxene and orthopyroxene. Microprobe chemical analyses are presented of all the phases mentioned. From the ratio of plagioclase to clinopyroxene the initial clinopyroxene probably formed at a depth greater than 35 km; if it crystallized at magmatic temperatures (1150°C) the depth must have been about 70 km. Exsolution took place at a pressure less than 6 kb after upthrusting of the rock to shallower depths. The great depth of initial crystallization has important implications for the conditions of origin of the ultramafic component of this granulite facies terrain.

Janggunite occurs as radiating groups of flakes, flower-like aggregates, colloform bands, dendritic or arborescenl masses in the cementation zone of the supergene manganese oxide deposits. The flakes average 0·05 mm. Colour black, lustre dull, streak brownish black to dark brown. Cleavage one direction perfect. H = 23, very fragile. Dmeas = 3·59, Dcalc = 3·58. Under reflected light anisotropic and bireflectant. No internal reflections. Etching reactions: positive - HC1, HNO3, SnCl2, H2O2, H2SO4 + H2O2. Chemical formula, on the basis of O = 14, or ideally . The mineral has an orthorhombic unit cell with a 9·324, b 14·05, c 7·956 Å, Z = 4, a:b:c = 0·663:1:0·566. Important diffraction lines are 9·34(s), 7·09(s), 4·62(m), 4·17(m), 3·547(s), 3·101(s), 2·597(w), 2·469(m), 1·863(w), 1·664(w), 1·525(m), 1·405(m), D.T.A. curve shows the endothermic peaks at 250–370°C and 955°C Infra-red absorption spectral curve shows vibrations at 515 cm−1, 545 cm−1, 1025 cm−1, and 3225 cm−1. The mineral and name have been approved before publication by the Commission on New Minerals and Mineral Names, I.M.A.