Iraqite, a new mineral of the ekanite group from northern Iraq, has the composition (Ln1·33 Th0·66x0·15) (K1·07y0·93) (Ca3·49 Ln0·35 Na0·16) (Si15·69 Al0·27) (O39·93 F0·07) where x = U, Pb, Zr, Fe, Mg, and Cu, and y is presumed to be vacant sites. It occurs in granite in contact with dolomitic marble. The colour is pale greenish yellow; H 4½ Dcalc 3·28 and Dmeas 3·27 (Berman balance), both corrected for minor impurity and non-structural water. Optically it is uniaxially negative with ω 1·590 and ε 1·585 though some sections show anomalous extinction up to 7°. Space group is P4/mcc with a 7·61±0·01 and c 14·72±0·02 Å. Strongest lines of the indexed powder pattern are 5·28(100), 3·31(100), 2·64(100), 7·36(80), 3·38(80), 3·40(60), 2·7(40), 7·62(30). Thermal data are given.

A nickel-bearing mineral belonging to the pyroaurite-sj~Sgrenite group has been found in a serpentinite rock near the village of Leslie, Aberdeenshire. X-ray powder diffraction data and electron-probe microanalysis indicate that the mineral has a three-layer rhombohedral structure with a probable formula near (OH)13CO3.4H2O. The mineral can therefore be described as nickeloan pyroaurite. It decomposes readily in mildly acid conditions and if inherited by serpentinite-derived soils could well be an important source of plant-available nickel.

Biotites from a number of granites have been analysed for major oxides and a wide range of trace elements. Their compositions are found to be typical of biotites from granite and to show element fractionation in presumed differentiation series. Estimates are made of the fugacity of oxygen and water during the crystallization of the granites. PH2O is found to increase slightly through the differentiation series, and fO2, for a temperature of 700°C is estimated to be between 10−18 and 10−12. Tin mineralization is connected with the igneous rocks and the relationship of tin in the micas to the rock compositions is described and the factors controlling the distribution of tin are discussed. The biotites have only up to 21 % of the tin of the granites. In general Sn increases in the biotites with decreasing temperature of equilibration and with increase in the degree of albitization of the granites. High Sn in biotites seems to be an indicator of potential mineralization.

The widespread ferristilpnomelane in Dalradian metabasites of the south-west Scottish Highlands has usually formed by secondary oxidation of primary ferrostilpnomelane, probably during weathering. Ferrostilpnomelane oxidizes readily in polished thin sections open to the atmosphere over a period of months, and microprobe examination of the resulting ferristilpnomelane suggests a change in the role of potassium in the structure during oxidation.

Four new chemical analyses are reported for riebeckites of the hypersolvus granites of Massachusetts and Rhode Island. Riebeckites of southern New England are enriched in Li+, which appears to substitute for Fe2+, with additional Na+ coming in to compensate for the charge imbalance.

A wide range of volcanic sublimates and alteration products from the Johnston-Lavis collection has been analysed for major elements plus copper, lead, and zinc. 'Aphthitalite' and 'natrikalite' from Mount Vesuvius and an 'alum' from the island of Vulcano all proved to be enriched in copper and selected analyses are tabulated. The process leading to copper and lead enrichment of the Vesuvian material may be vapour phase transport as chloride followed by sulphation on sublimation. It is suggested that the source of the copper found in the alum sample from Vulcano could be of interest to economic geologists.

Differential thermal analysis of a rapidly reversible transition in carnegieite to 7 kbar shows the transition temperature increases from ⪝ 707°C (on heating) at I bar with initial slope ≈ 8·0 deg kbar−1 and anomalous curvature (d2T/dp2 > o), with hysteresis between heating and cooling signals that decreases with pressure. DTA of rapidly reversible transitions in nepheline shows the very subtle transition near 185°C (on heating) at 1 bar decreases with pressure to ≈ 170°C near 2-3 kbar and hardly varies in temperature up to 6 kbar; and the higher temperature transition increases from ≈ 872°C (on heating) at 1 bar with slope ≈ 25 deg kbar−1, to 5 kbar, with the hysteretic interval remaining essentially unchanged in the investigated range.

A layered aipine-type peridotite, of pre-Scourian age(?), has been metamorphosed in the granulite facies then partially retrogressed to greenschist facies assemblages. Following granulite facies metamorphism of the dunite-harzburgite peridotite, granitization and metasomatism modified the peridotite by adding calcium and generated olivine-tremolite rocks. Anthophyllite-rich rocks developed from localized orthopyroxene-rich zones. The main epoch of serpentinization followed after tremolite formation and removed a portion of the calcium previously added, but with negligible effect upon the original trace-element content. Between tremolite generation and the main period of serpentinization greenschist facies assemblages formed. The layered rocks possess a repetitive, chemical variation normally attributable to basic igneous processes, although they may have formed either by vein metasomatism or by metasomatism of a disrupted layered igneous series. Twelve rock and five mineral analyses are presented, and trace element data for twenty-one rocks.

A study has been made of a large clinoptilolite deposit in the Lesser Caucasus (Azerbaidzhan SSR). The geological conditions have been examined and a number of samples investigated by optical, electron-microscopic, chemical, X-ray, thermal, and infra-red methods. Based on these investigations and on comparison with previous literature, mineralogical, chemical, and geochemical conclusions are drawn and conditions for clinoptilolite genesis are considered.

A muscovite that contains iron almost entirely in the ferric form has been studied by M6ssbauer spectroscopy. It is established that Fe3+ ions in the sites with cis hydroxyl groups have similar parameters in both muscovite and biotite. By assuming that Fe2+ ions will also have similar parameters for these sites in both minerals the M6ssbauer results of other workers have been reinterpreted. This new interpretation, which is in complete agreement with the X-ray structural analysis of Radoslovich (1960), indicates that in muscovite the sites with cis hydroxyl groups are filled in preference to those with trans hydroxyls. These sites are occupied primarily by trivalent ions. There is possibly a preference for divalent ions by the unique sites with trans hydroxyl groups, but occupation of these sites appears to occur only when the other sites have been filled.