Glaukosphaerite, a new secondary basic copper-nickel carbonate was first determined and described from Widgiemooltha (31° 30′ S., 121° 34′ E.), Western Australia, by R. C. Morris at the W.A. Government Chemical Laboratories in 1967. The mineral has since been found at the nickel mines at Kambalda, Windarra, Scotia, Carr Boyd Rocks, and St. Ives, Western Australia, and is apparently an indicator of copper-nickel sulphide mineralization. The name is derived from the colour and spherulitic formation. Associated minerals are goethite, secondary quartz, paratacamite, gypsum, nickeloan varieties of magnesite and malachite, and clays. Glaukosphaerite also fills joints in fresh basic rocks.

The type material is from Hampton East Location 48, 3 km N. of the Durkin Shaft, Kambalda. Glaukosphaerite is monoclinic, a 9·34 Å, b 11·93 Å, c 3·07 Å, β 90–1°, space group indeterminate, c axis disordered, six strongest X-ray powder lines are 2·587 (10b) 201, 3·68(7b) 220, 2·516(4) 240, 211, 5·04(3) 120, 2·124(3b), 1·473(3). The mineral occurs in green spherules of fibres cleaved and elongated along c, D = 3·78 to 3·96 increasing with Cu, is brittle, H. 3 to 4, and has dull to subvitreous to silky lustre.

α 1·69–1·71 green, β ≈ γ 1·83–1·85 yellow-green, α:[001] 7°.

Chemical analysis on the type material, D 3·78, containing 0·5 % goethite impurity and minimal inseparable malachite, gave CuO 41·57, NiO 25·22, CoO 0·07, ZnO 0·02, Fe2O3 0·47, MgO 1·23, SiO2 < 0·01, CO2 21·70, H2O+ 9·85, H2O− < 0·01, sum 100·13%. After deduction of goethite the unit cell contains 4[(Cu,Ni,Mg,Co)1.74C0·96H2·12O4·73]. This unit-cell content is deficient in metal ions and oxygen and contains excess H, when compared to 4[(Cu,Ni)2(OH)2CO3]. Two analyses of malachite-bearing glaukosphaerite from Widgiemooltha and Carr Boyd Rocks show the same deficiencies and excess not previously recorded in malachite, rosasite, or aurichalcite analyses. Glaukosphaerite, 4[(Cu,Ni)2(OH)2CO3] is the nickel analogue of rosasite 4[(Cu,Zn)2(OH)2CO3].

From results based on X-ray rotation patterns of oriented rosasite fibres from Sardinia and Durango with supplementary electron-microprobe studies and Guinier powder-film data, the authors consider glaukosphaerite and rosasite to be separate mineral species from the related malachite, 4[Cu2(OH)2CO3].

Type material is preserved in the government collection at the Government Chemical Laboratories, Perth, Western Australia.

Cesbronite occurs at the Bambollita mine, near Moctezuma, Sonora, with a variety of other tellurites. The colour is ‘green beetle’ (R.H.S. 135-B) with a pale streak. H 3; Dmeas 4·45±0·2. Crystals are orthorhombic 2 mmm with a 8·624 Å, b 11·878, c 5·872 (all ± 0·016 Å); space group Pbcn. For Z = 2 the calculated density is 4·455 g/cm3. The strongest powder lines are 5·934 (100), 3·490 (92), 4·889 (71), 2·358 (70), 2·379 (38), 1·592 (34), 2·156 (28), and 1·698 (27). Electron-probe analysis gave: CuO 50·3 %, 50·3, 49·8, 49·4; TeO2 39·3 %, 39·2, 38·6, 38·6. Water determined gravimetrically 11·0 %. This gives Cu5(TeO3)2(OH)6.2H2O.

Cesbronite is pleochroic with absorption γ ≈ β ≫ α. Optically positive with 2Vγ calc. 72°; α 1·880 ‖[100], β 1·928 ‖[001], γ 2·029 ‖[010].

The compositions of feldspar pairs crystallized from stoichiometric alkali feldspar gels with water at PH2O ≈ 1 kbar in runs of up to 3000 hours' duration vary with Na:K in the starting material. This is because, for most bulk compositions, rapid nucleation in the gel leads to growth of one feldspar phase outside the solvus. The composition of this initial feldspar phase can be thought of as reflecting the configuration of the liquidus-solidus curves in the system Ab-Or. In general, the attainment of the stable equilibrium solvus (binodal) requires that one phase approach the binodal from outside; for compositions with < 30 mole % Or this phase becomes more potassic with time, with > 30 mole % Or, more sodic. Homogeneous gels of bulk composition Ab70Or30 initially crystallize feldspar pairs inside the binodal, which rapidly (< 17 hours) unmix to define a solvus-like curve (probably the spinodal, with an apparent critical point at 602 °C and 31 mole % Or) and then unmix slowly, giving a solvus after 3000 hours with a critical point at 657 °C and 36 mole % Or.

Because this curve has been approached from two directions it is the best approximation to the binodal (metastable only with respect to Al-Si order) obtained. It is similar to the 2 kbar ‘peralkaline’ solvus of Orville, 1963, provided an adjustment for pressure of 16 °C/kbar is made. Differences between solvi determined by Luth and Tuttle (1966) for ‘non-stoichiometric’ bulk compositions may reflect differences in initial crystallization behaviour, as may the breaks in the solvus limbs suggested by Luth et al. (1974).

Microprobe analyses of Ca-rich pyroxenes crystallized in the melting ranges of a magnesian alkali basalt, a transitional basalt, an olivine tholeiite, a tholeiitic andesite, and an augite leucitite at pressures between 8 and 45 kb show complex variation. Ca-poor pyroxene precipitated only from the alkali basalt at pressures between 14 and 18 kb. Pyroxene falling near the Di-Hed join in the pyroxene quadilateral formed at all pressures and temperatures from the leucitite, whereas ‘Ca-rich’ pyroxene crystallizing from the other four compositions was Ca-poor augite to sub-calcic augite. The liquidus Ca-rich pyroxenes all show rising Al and Na and falling Ti with increasing pressure and temperature. Other elements show complex behaviour; all but the leucitite pyroxenes tend to make temporary excursions of solid solution towards Ca-poor pyroxene at intermediate pressures, returning to more Ca-rich compositions at high pressures. At sub-liquidus temperatures Na and Ti consistently rise with falling T at constant P and also with rising P at constant T in these pyroxenes. The behaviour of the other elements in these circumstances depends on the nature of the coexisting phases.

Fe/Mg distribution between Ca-rich pyroxene and liquid, in the form

has a constant value of 0.29 for three separate bulk compositions at widely differing temperatures and pressures. Distribution coefficients for Mg and Fe between pyroxenes and coexisting garnets at high pressures are very similar to those found in garnet pyroxenite xenoliths from Oahu, Hawaii. Systematic shifts in the apparent stoichiometry (all Fe taken as Fe2+) of the augite leucitite pyroxenes are thought to indicate that they have considerable Fe3+ contents at low pressure, decreasing as P rises. If so, they show a strong negative correlation between Na and Fe3+, which negates the customary practice of forming acmite before jadeite component when recalculating the analyses of high-pressure pyroxenes.

The sets of pyroxenes crystallized from each composition show consistent trends when plotted on such diagrams as jadeite vs Ca-Tschermak's ‘molecule’, which have often been used in attempts to discriminate natural pyroxenes formed in differing P-T environments. However, these new data show clearly that the bulk chemistry of the magma has a predominating influence on the composition of the pyroxenes crystallizing from it. Unless it is certain that a suite of natural pyroxenes have all precipitated from the same magma, it is probably pointless to attempt to deduce the relative P-T conditions of their formation from their major element chemistry.

Transmission electron images of fine-grained micas from various clay deposits exhibit lath-shaped units arranged in modes similar to the stacking of layers in different mica polymorphs. Micas in a Georgia bentonite display two sets of parallel laths intersecting at an angle of 120°. Selected area electron diffraction (SAD) of these micas gives a sharp spot pattern indicating a perfect registry between the lattices of individual laths. Furthermore, the SAD pattern has an intensity distribution similar to that of a 2M1 dioctahedral mica. Another mica in an India bentonite shows one set of parallel laths with an intensity distribution expected from a IM biotite. Some of the micas in the Marblehead illite exhibit three sets of parallel laths in a trigonal arrangement similar to the stacking in 3T mica.

The formation of porphyroblasts by replacement and displacement of pre-existing S surfaces is examined in the light of textural evidence displayed by sediments hornfelsed by the Bushveld Igneous Complex. Helicitic biotite, staurolite, and cordierite all show replacement and displacement textures, the former being more common. The evidence indicates that porphyroblasts arc capable of creating local pressure differences that disturb the pre-existing banding, even in hornfelsed rocks that have suffered neither regional metamorphism nor orogenic movement.

Peridotitic rocks in the Massif du Sud, southern New Caledonia, have suffered about 30 % serpentinization. Optical studies combined with X-ray and chemical analyses indicate that chrysotile and lizardite are the dominant serpentine species present. Serpentinization probably occurred during emplacement of the Massifs in their present overthrust position.

In contrast with some other hydrous aluminum phosphates, vashegyite is crystalline. Simultaneous application of several assumptions leads to the hypothesis that it has a structure analogous to that of kaolinite, and thus contains tetrahedral sheets, n[X2O5], where X is both P and H3 (in lieu of Si). Thus, the theory involving [HXO4] is extended from phosphates with isolated tetrahedral groups [XO4] and framework linkages [XO2] to sheet linkages [X2O5]. Kingite also may have a kaolinite-like structure.

The potash feldspar in the charnockites is orthoclase and they are inferred to have been formed around 700 °C. A twin-law study of the plagioclase indicates an igneous origin of the charnockites and pyroxene granulites. The KD values of the coexisting pyroxenes in the granulites are appropriate to equilibrium at 670 °C. A substantial substitution of A1 for Si in the values of the coexisting pyroxenes in the granulites are appropriate to equilibrium at 670 °C. A substantial substitution of A1 for Si in the Z group in all mafic minerals studied also indicates relatively high temperatures of formation. Almandine is pyroperich, a result of high pressure. The charnockites and pyroxene granulites are inferred to be formed under conditions of high pressure and temperature.

Investigation of the mineralogy and paragenesis of the fluorspar flat at Masson Hill, Matlock, Derbyshire, shows the mineralization to be a combination of void infilling and metasomatic replacement. The main paragenesis is of the non-sulphides, fluorite, baryte, and calcite accompanied by a sequence of sulphides, bravoite, pyrite, marcasite, chalcopyrite, sphalerite, and galena. A wide range of secondary minerals occur in the oxidation zone.