The application of classical nucleation theory to the initiation of crystal growth in glasses is discussed. Its application to experimental results obtained for the rate of nucleation in three types of glass, one showing nucleation separately from crystal growth, another showing simultaneous nucleation and growth, and the third showing crystal growth after metastable liquid/liquid phase separation, is then described. Recent work on the kinetics of unmixing in glasses is outlined. The influence of so-called ‘nucleating agents’ in the glasses described appears to be exerted through changes in the anionic structure.

Conditions necessary for exchange between lattice OH groups and D2O in expanding layer silicates are reported. From spectral changes in the 200–1200 cm−1 region resulting from this exchange, in-plane librations of OH co-ordinated to (A1A1), (A1Mg), (A1Fe3+), and (MgMgMg) have been identified in montmorillonite, beidellite, saponite, hectorite, and vermiculite. Both in-plane and out-of-plane librations have been identified for pyrophyllite and celadonite, from comparison of synthetic specimens containing OD with natural or synthetic OH forms. Comparison of hydrogen and deuterium forms of Mg- and Ni-talcs leads to the identification of translational and librational OH vibrations.

Techniques associated with temperature control and measurement in quench furnaces are described and a study made of calibration problems. Systematic temperature errors as great as 30°C in published results from separate laboratories are explicable. A comprehensive redetermination of temperatures of invariant equilibria in systems containing CaO, MgO, Al2O3, SiO2, Na2O, Fe-O2, has been initiated and the results to date are presented, including approximate determinations of three invariant equilibria in the system CaO-MgO-Al2O3-SiO2 involving liquid, monticellite, spinel, and two of merwinite, periclase, and forsterite, which are important in the melting of magnesia refractories, and precise determinations of the three newly recognized invariant equilibria involving liquid, spinel, diopside, and two of forsterite, melilite, and anorthite.

Bideauxite is a new mineral found in specimens from the Mammoth-St. Anthony mine, Pinal County, Arizona. The composition is Pb2AgCl3(F,OH)2 with Pb, Ag, Cl, F by duplicate wet analyses. Z = 16, G. calc. 6·256, meas. 6·274 (at 24·2 °C). Crystals are isometric hexoctahedral with a 14·132 Å. Space group Fd3m. Crystals show a, o, d, m {113}, μ {114}, n {112}, φ {116}, and {029} in decreasing order of importance. Colourless, transparent with white streak. Isotropic with nD 2·192. le, almost sectile, withc onchoidal fracture. H = 3. Turns pale lavender in strong light. Low M.P. B.P. Decomposes in acids and warm NH4OH. Bideauxite is an oxide zone mineral found with leadhillite, matlockite, and anglesite. May alter to cerussite.

Cathodoluminescence, produced by electronic bombardment in the microprobe, can serve to indicate the nature and distribution of elements present in amounts below the normal detection limit of the probe. This is illustrated by a study of specimens of blende from various localities.

Dadsonite was previously described without a name: (mineral Q) from Yellowknife, N.W.T.; (mineral QM) from Madoc, Ontario, and Pershing County, Nevada. Material from a fourth locality (Wolfsberg, Germany) yields good powder patterns, identical with those of QM, and single crystal data identical with those for Q.

Microprobe analysis of the Nevada and Wolfsberg samples gave, respectively, Pb 49·3, 50·8; Sb 31·7, 31·8; S 20·7, 20·3; sum 101·7, 102·9 %, giving Pb11Sb12·0S29·8 and Pb11Sb11·7S28·4, ideally Pb11Sb12S29 or 11PbS·6Sb2S3. Dadsonite is acicular [010], monoclinic, space group P2, Pm, or P2/m, with a 19·05, b 4·11, c 17·33 Å, β 96° 20′, Z = 1, Sp. gr. 5·76. The strongest lines of the X-ray pattern are 3·78 (7), 3·62 (6), 3·38 (10), 2·84 (7), and 2·79 Å (6).

Complete lattice parameters have been determined at a series of temperatures up to 950 °C using a furnace on a powder diffractometer for six synthetic supposed equilibrium albites, a nonequilibrium albite, two natural albites, and a heat-treated natural albite. The supposed equilibrium albites were prepared hydrothermally by MacKenzie (1957) for long periods of time and reached or nearly reached a state of no further change at their temperatures of synthesis between 500 and 1000 °C. A crystal of natural albite and three crystals of heat-treated natural albite were studied by high-temperature, single-crystal methods on a Buerger precession camera up to 1000 °C for comparison.

The lattice angles for each albite decrease smoothly with increasing temperature; the a-axis and the volume increase smoothly with increasing temperature. The rates of change increase with increasing temperature. The c and in some cases the b-axes appear to decrease initially in the range 25–300 °C and then subsequently increase. The thermal dilatation is highly anisotropic—the change in a is about twice that in b and about six times that in c over the whole range 25–850 °C. The effect of a temperature rise on the lattice parameters of the albites is very similar to the effect of the substitution of potassium on the room-temperature parameters.

Plots of α* against γ* for each albite at a sequence of temperatures up to 950 °C fall on nearly straight parallel lines, all albites becoming less oblique (triclinic) with increasing temperature. Of the equilibrium albites, only the one synthesized at 1000°C becomes monoclinic below the melting point. The ratio d010/d001 or c*/b* is a measure of order in the albites and does not vary with temperature. The similar behaviours of this ratio and of other lattice parameters as a function of the temperature of synthesis confirms the two-step ordering process in albite.

The cell parameters of 35 members of the arfvedsonite-eckermannite series and catophorites (17 from the literature, 18 newly determined) are presented and an attempt made to relate them to chemical composition. In general, all parameters (including β, obtuse) decrease from arfvedsonite to eckermannite, but for different reasons: a, b, and β (very slightly) as the Mg: Fe2+ ratio and F increase; c as Fe3+ decreases. The apparent decrease in a and b with high Li is coincidental, due to its strong correlation with F, which varies inversely With (OH). In addition, b is increased by high Ca and slightly reduced by high A1.

Also, the empirical and calculated curves relating MgO and total iron as Fe2O3 (weight %) with the Mg ratio, 100 Mg/(Mg + Fe2+ Fe3+ + Mn), for all amphibole groups are given, as a rapid method of obtaining an estimate of the Mg ratio.

The full lists of possible hkl values for an arfvedsonite and an eckermannite are enumerated up to 45° 2θ, Cu-Kα, to illustrate the difficulty in indexing X-ray photographs and diffractometer charts of this group.

Three of the members of the plagionite group, fülöppite Pb3S8S15, plagionite Pb5Sb8S17, and semseyite Pb9Sb8S21, show linear correlations of cell volume and density versus PbS:Sb2S3 mol ratios. This relationship can be used better to define the nature of the fourth member of the group, heteromorphite, Pb7Sb8S19. The cell dimensions derived for heteromorphite are a 13·60, b 11·93, c 21·22 Å, β 90° 50′.

Quantitative data are presented for the kinetics of crystal growth in an aluminosilicate glass to which a few wt % of a transition-metal oxide had been added. The composition of the base glass was CaO 3o, MgO 2, Al2O3 15, SiO2 53 wt %, to which the oxides of iron, vanadium, chromium, or zinc were added. Glasses were prepared with a range of high to low valency ratios in cases where the transition metal oxide could exist in two or more oxidation states.

Small quantities of Fe2+, Fe3+, Zn2+, V3+, V4+, and V5+ were all found to increase the kinetics of crystal growth from the glass phase. The magnitude of the effect is compared with additions of Mg2+ to the glass. Cr2+, Cr3+, and Cr6+ were found to decrease the rates of crystal growth. Values for the apparent activation energy for crystal growth ranged from ∼50 kcal/mole to ∼150 kcal/mole. The high values were found to be of the same order of magnitude as that for the activation energy for viscous flow in the glass at the crystallization temperature.

The results are interpreted in terms of the structure of the glasses and current theories on the rate of crystallization of glasses.

The fall of a shower of meteorites numbering several hundred fragments at Wiluna, Western Australia, on the night of 2 September 1967, has been investigated. Although the dispersion ellipse had been largely obscured by removal of fragments before a party of scientists were able to make a field investigation, it has, nevertheless, been possible to make a reasonable estimate of the shower distribution pattern. In spite of this removal of fragments, a number of pieces of meteorite were still found in situ. The bulk of the total recovery is in the collections of the Western Australian Museum, and the physical characteristics of these masses and their petrography is described. In all, some 490 individual fusion-crust coated stones and a large number of broken stony fragments are known to have been recovered. The meteorite is an olivine bronzite chondrite remarkably rich in discrete nodules of nickel iron, up to an inch across, commonly aggregated with troilite. A full chemical analysis of this fresh meteoritic material has been supplied by the British Museum (Natural History).

Hodrushite, a new sulphosalt of copper and bismuth, was found in the Rosalia ore vein at Banská Hodrušá near Banská Štiavnica, Czechoslovakia. It has chemical composition Cu8·12Bi11·54Fe0·29S22 (as determined by electron-microprobe method) close to Cu8Bi12S22. Symmetry is monoclinic, space group A2/m, lattice constants a 27·21, b 3·93, c 17·58 Å, β 92° 9′, measured density 6·35, calculated density 6·45 g/cm3. Microhardness 200 kg/mm2, anisotropic, weak bireflectance, creamy with pinkish tint, maximum reflectivity about 6000 Å. Crystals needle-shaped and striated along [010], colour steel-grey, quickly tarnishing to bronze. Associated with quartz, hematite, and chalcopyrite. Closely related to cuprobismutite.

The position of the 01 X-ray reflection in albite varies with the degree of Al/Si ordering. This is also true for binary plagioclases but the 01 reflection for high-temperature plagioclases is constant and therefore independent of anorthite content. For plagioclases of ternary composition grown in a hydrous silicate melt, the position of the 01 reflection gives a good estimate of the orthoclase content when a determinative curve is used that was originally drawn from data on high-temperature synthetic binary alkali feldspars.

When gels and glasses of alkali feldspar composition are crystallized hydrothermally below their solidus the crystals present when crystallization is incomplete do not have the same Na:K ratio as the starting material but bear a relation to the starting material analogous to that between crystals and liquids coexisting at the liquidus. This effect has been investigated in the temperature range 700–850 °C at water-vapour pressures between 5000 lb/in.2 and 30000 lb/in.2 Fractionation and normal zoning of crystals may, in principle, occur within fixed bulk compositions held under isothermal, isobaric conditions.

Electron probe analyses have been made of eight kaersutites from San Carlos, Arizona, and one from Kakanui, New Zealand; also of olivine, clinopyroxene, ilmenite, and spinel from San Carlos. There is not as yet adequate evidence that the kaersutite is an upper mantle phase.

Data are presented from cobaltite (CoAsS), gersdorffite (NiAsS), and ullmannite (NiSbS) for cell size, compositional zoning, mineralogical association, X-ray diffraction powder intensities, and optical anisotropy. The presence of powder X-ray diffraction reflections 001 and 011 are related to the crystal structure type. The amount of distortion from cubic symmetry is related to the 001 reflection intensity and also to the optical anisotropism strength. These properties are related approximately to the thermal stability of the distorted crystal structure. This thermal stability increases with the substitution of cobalt for nickel, which decreases the cell size. An order-disorder change occurs before the distortion release in non-cubic gersdorffite (P1) with a large cell size, whereas only a distortion release is observed in cobaltite (Pca21) and non-cubic gersdorffite (P1) with a small cell size. Glaucodot (Co,Fe)AsS converted to cobaltite at 620 C. No evidence was found to relate optical anisotropism of pyrite to deviations from cubic symmetry.

Staringite, (Fe,Mn)0·5(Sn,Ti)4·5(Ta,Nb)1·0O12, occurs as inclusions in tapiolite from pegmatites at Seridózinho and Pedra Lavreda, Paraiba State, NE. Brazil. An indexed powder pattern is presented. The mineral is tetragonal with a 4·742 Å and c 9·535 Å, and most probably has a ‘trirutile’ structure. Electron-microprobe analysis yielded Ta2O5 21·5%, Nb2O5 1·8, SnO2 73·3, TiO2 0·03, FeO 3·7, MnO 0·3, sum 100·6%. Dcalc 7·17. Micro-indentation hardness (load 100 g) 1033–1187 kg/mm2; reflectivity at 470 nm (R0) 12·8 to (R′e) 14·5%, at 546 nm 12·1–13·9, at 589 nm 12·0–13·7, and at 650 nm 11·8–13·6; staringite is uniaxial positive.