Wroewolfeite is a new mineral from the Loudville lead mine in Loudville, Massachusetts, U.S.A. The mineral occurs as blue, monoclinic crystals, twinned on {001}, very similar in appearance to posnjakite and langite. It is formed as small isolated pinacoidal crystals (up to 1.0 mm) implanted on covelline and chalcosine. There are three cleavages of equal facility of production. The cell dimensions are a 6.058 Å, b 5.654 Å, c 14.360 Å, β 93° 28′, space group Pc or P2/c. The strongest diffraction lines (in Å) are 7.152 (100), 3.581 (70), 2.628 (35), 2.004 (30), 2.431 (20), 2.379 (20), 2.278 (20). Electronmicroprobe analysis gives CuO 64.22 %, SO3 16.48 %, water by difference 19.30 %. Empirical cell contents are Cu7.88(SO4)2.00(OH)11.76.(H2O)4.22 or Cu4(SO4)(OH)6.2H2O with Z = 2. Wroewolfeite is strongly pleochroic with a light blue, β deep greenish blue, and γ, medium greenish blue. Absorption β > γ ≫ α. The mineral is biaxial with α 1.637, β 1.682, and γ 1.694, 2Vα = 53° The name is for C. Wroe Wolfe, American crystallographer, educator, and philosopher.

Examination of some pyroxenite nodules from the Jagersfontein kimberlite shows that they have suffered variable deformation followed by different degrees of recovery. Most interes~ting of the nodules is the 'diallage rock', which consists of highly sheared and broken lamellar crystals of diopside containing exsolved enstatite. Petrographic evidence indicates a pre-tectonic exsolution of enstatite and a syntectonic exsolution of pyrope-almandine from enstatite. Deformation occurred in the mantle, prior to incorporation of the nodule in the kimberlite. Compositions of pyroxenes from the diallage rock suggest it re-equilibrated at a temperature of 1000° and at a pressure of about 35 kb. Olivine and phlogopite, accompanied by serpentine, occur only in broken kink-bands in the diallage rock and they are considered to be of secondary origin, precipitated from kimberlite magma at temperatures near 700°

Large albitite bodies associated with explosive brecciation, fenite aureoles, intrusive carbonate rocks, olivine dolerites, and copper mineralization are described from the Dead Sea rift region in the south-eastern Sinai Peninsula. The main carbonate phases comprise breunnerite and dolomite with actinolite the main phase in the fenites. Field and isotopic evidence indicates that the intrusive carbonate rocks are of carbonatitic origin. The cogenetic, almost monomineralic main phases can be attributed to fractional crystallization and liquid immiscibility acting on a highly gascharged, slow-cooling gabbroic magma. The complex, which is probably of Cretaceous (or older) age, appears to be related to early continental separation along the Dead Sea branch of the African rift system. The porphyry-type copper deposits resemble others that are located along crustal accretion (Iceland) or subduction (Chile) zones.

Eocene tholeiitic basalts occur throughout the length of New Caledonia where their emplacement preceded that of the peridotite massifs. In the south, two areas of basaltic rocks are intimately associated with Eocene sediments, which have been overridden by the peridotites. The aphyric, holocrystalline basalts consist of plagioclase, clinopyroxene, titanomagnetite, and minor quartz together with their abundant alteration products, which include epidote and uralite. The chemical compositions of these rocks fail to show agreement with oceanic tholeiitites, as suggested by earlier writers, although strong similarities exist with the basalts of the Papuan Ultramafic Belt.

Mercury has been determined by radiochemical neutron-activation analysis in nineteen representative rocks from the Skaergaard intrusion and in the separated cumulus minerals of five. The chilled marginal gabbro contains 0.23 ppm Hg, values in the Layered Series rocks ranging from 0.07 to 0.34 ppm, in one exceptional case reaching 1.23 ppm Hg. There is a tendency for mercury to be more abundant in leucocratic than in average or melanocratic rocks at a similar horizon. Somewhat higher levels of mercury are found in the granophyric rocks at the top of the intrusion.

Apart from a weak and sporadic tendency to be preferentially enriched in plagioclase, the distribution of mercury between the various cumulus phases is fairly uniform and it is thought to occur as uncharged atoms mainly occupying spaces resulting from lattice defects and imperfections rather than in specific structural sites.

The distribution pattern of mercury in the intrusion appears to be determined by its high volatility and chemical inertness; no real evidence of any chalcophile character is observed.

Aluminous Ca-rich clinopyroxenes (5.95-7.63 wt % Al2O3) are next in abundance to leucite in the basic alkaline potassic lavas from Monte Somma and Vesuvius, Italy, and occur as phenocrysts (1 to 7 mm), micropbenocrysts (< 1 mm), and groundmass granules. Zoning of various types is a conspicuous feature in these pyroxenes. Optical and chemical data are presented and a comparison is made between these pyroxenes and similar ones from alkali basalts. It is known from published data that Al2O3 fluctuates strongly in the oscillatory zones of Vesuvian pyroxenes. This can be explained as due to temperature variation in the magma, to magma variation in silica content due to contamination, to oscillations in leucite precipitation, or to a combination of these factors. Of these three factors, oscillations in leucite precipitation, as it appears, would be more effective than the others since it would have a greater control over Si/A1 availability in the magma.

Chemical analyses of eleven garnets from orthogneisses and related pegmatites, belonging to the Upper Swat Hornblendic Group, Pakistan, are presented along with the petrographic descriptions of the host rocks. The garnets show dominant almandine content, followed by grossular pyrope, spessartine, and andradite, in order of relative abundance. One garnet sample is different from the rest in having higher andradite and spessartine contents and higher refractive index, and is also different in habit. This is the first detailed study of garnets from Pakistan.

While undergoing 'dry' homogenization at 980°C the 2̄01 X-ray reflections of sodic lowalbite- microcline microperthites show that phase compositions recapitulate (but in a reverse timesense) the unmixing history of ordered feldspars about a solvus with a critical composition near 26 mole per cent KAlSi3O8.

The garnierite, which occurs in the oxide zone overlying a nickel sulphide deposit, consists of talc-like and serpentine-like components, with the former predominating. Chemical and electron-probe analyses give NiO contents ranging between 39.6 and 43.9 weight %.

The volatilities of SiO2, Na2O, and Fe2O31 increase with increasing thermal function within the range 1600 to 2100°C during the melting of a sandy-silty clay. The remaining melt is to some extent enriched in Al2O3, K2O, CaO, and MgO. Chemical analyses of the sandy-silty clay, of the glasses melted from the latter, of the silicate material evaporated and newly condensed and their correlation with increasing thermal function and bulk density of glasses, as well as with the hitherto known quantitative data on moldavites, testify to the fact that in moldavites evaporated and newly condensed silicate material substantially prevails over material that passed directly from a solid to a fluid state. Evaporation of the silicate material from the rocks of the impact crater caused a significant change in relations between major oxides compared to the original relations in the source rocks. Thus, the hypothesis that tektites are directly remelted rocks of the Earth's crust, based on over-all chemical similarities of tektites and some rocks in major oxides, appears incorrect.

The effect of heat treatment in air at temperatures from 200°C to 1000°C of two Cornish biotites has been studied using the M6ssbauer effect in 57Fe. One of the micas was also studied after heating in vacuo.

Progressive changes in the Mössbauer spectra of the materials after heat treatment can be correlated with the following processes: Oxidation of Fe2+ ions in isolated octahedral sites to give Fe3+ in the co-ordination Fe3+(OsOH); oxidation of Fe2+ ions in adjacent a-octahedral (cis OH−) sites to give Fe3+(O6); and oxidation of Fe z+ in adjacent a and b (trans OH−) sites to give either Fe3+(O5OH) or Fe3+(O6) depending on whether a shared hydroxyl group remains intact or otherwise (these processes occur at temperatures below 500°C Also, at higher temperatures, dehydroxylation of Fe3+(O5OH) to give more Fe3+ in the Fe3+(O6) configuration. Finally, in the temperature range 900 to 1000°C structural breakdown yielding α-Fe2O3 as the iron-containing phase.

The results and interpretation are in good agreement with thermogravimetric data and with a previous infra-red study. The mechanism of charge diffusion in the lattice during oxidation is discussed in the light of the results.

Two clay samples originating in the kaolinized granite area near St. Austell, Cornwall, have been examined by Mössbauer spectroscopy. The iron-containing impurity in the sample with a red discoloration (sample A) has, by measurement of the hyperfine magnetic field, been identified as hematite. In the case of sample B, which was yellow in colour, preliminary Mössbauer work indicated β-FeOOH as the impurity, but detailed measurements of hyperfine field and Nöel temperature, when compared with similar results for a synthetic β-FeOOH sample, suggested otherwise. X-ray and chemical work suggested that the iron-containing phase in sample B is goethite, α-FeOOH in which some substitution of Al+3 for Fe3+ has occurred; the Mössbauer data are consistent with this conclusion. Both clay samples exhibited superparamagnetic behaviour and this has been utilized to obtain rough estimates of the mean radius of the particles of the iron-containing impurity. These were 117 Å for the α-Fe2O3 in sample A and 270 Å for aluminian α-FeOOH in sample B.

A simple and easy-to-use miniphotometer has been designed; the expense involved amounts to only a fraction of that required for large commercially available microphotometers.

The instrument can be employed for routine investigations and for teaching reflected light microscopy in conjunction with standard reflected light microscopes.

The reflectance of grains down to 50 μm size can be measured in white and monochromatic light employing continuous band and line interference filters. The systematic error does not exceed 1.5 % of the values measured. The only aspect that distinguishes the miniphotometer from larger instruments is the limitation of spot size. A comprehensive test programme including comparative sets of measurements on a Zeiss MPM spectral microphotometer has shown that the results obtained by both instruments coincide well.