Embreyite is a new mineral that has been found only in old specimens collected at Berezov, Siberia. The composition is Pb4·97(CrO4)2·00(PO4)1·91.0·75H2O, or Pb5(CrO4)2(PO4)2. H2O based on both wet and electron-probe analyses. Z = I, Dmeas 6·45, Deale 6·41. Crystals are monoclinic with a 9·755 Å, b 5·636, c 7·135, β 103°5′ the space group may be P21/m. No single crystals were found. α = 2·20, β = γ = 2·36. Colour in various shades of orange with a yellow streak. H = 3½; no cleavages observed. Occurs with vauquelinite, crocoite, and phoenicochroite in the oxide zone assemblage from Berezov.

Insizwaite from Waterfall Gorge, Insizwa, is a new mineral with the composition Pt1·00Bi1·35Sb0·57. The name is for the locality and is to be applied to the end member PtBi2. The analysed material is an antimonian variety. The mineral is cubic, the unit-cell for the antimonian variety has a 6·625 (2) Å, probable space group Pa3, calc. D 12·8 g/cm3. The strongest lines on the X-ray diffraction powder pattern are: 2·96 (8) 210; 2·70 (8) 211; 2·34 (5) 220; 1·99 (10 311; 1·774 (7) 321; 1·433 (5) 421; 1·277 (6) 511, 333; 1·171 (6) 440; and 0·862 (7) 731. Under reflected light the mineral is white (in air and in oil) and is isotropic. Reflectance measurements at 470, 546, 589, and 650 nm gave 61·1, 60·0, 60·6, and 61·7 %. Micro-indentation hardness values range from 488 to 540 (av. 519) kg/mm2 with a 25 g load.

New data are presented for niggliite from the type locality and for synthetic PtSn.

The structural states of alkali feldspars from the eastern end of the Galway Granite show transitions from orthoclase to microcline as a result of late deformation. Analyses of twenty samples for SiO2, Al2O3, TiO2, Fe2O3, CaO, Na2O, K2O, S, Cu, Zn, Ga, Rb, Sr, Ba, and Pb agree with previously determined orders of entry of elements into the ‘alkali site’. A relationship between this order of entry and the melting points of feldspar end-members is discussed.

The field relations, mineralogy, and petrography of a small Tertiary ultrabasic sheet are briefly described. Chemical analyses show that compositional variations exist within the intrusion and electron-probe analyses demonstrate that optically undetectable zoning is present in the olivine. Throughout the intrusion, which is composed primarily of forsteritic olivine, calcic plagioclase, and clinopyroxene, there is a differential distribution of olivine. This distribution is attributed to flow differentiation during intrusion followed by gravitative sinking of olivine crystals.

Fenitized quartzites are described from three localities around the Borralan alkaline igneous complex. Chemical and electron-probe analyses of amphiboles, pyroxenes, micas, and feldspars are given. Early-formed amphiboles are calcic, but these are replaced by alkaline varieties with increasing fenitization. Rock analyses indicate a ‘straight line’ rate of increase of Ti, Fe2+ + Fe3+, Mg, Al, K, and a more variable increase of Ca and Na atoms, at the expense of Si atoms. The simple composition of the unaltered quartzite allows the accurate calculation of bulk changes during fenitization. The final product of the alkali metasomatism is a syenite lying close to the albite-orthoclase minimum though the primary source of the fenitizing fluids was probably a highly potassic magma.

Talc-kyanite-quartz schists, Mg-chlorite-kyanite-quartz schists, kyanite gedritites, and kyanite-bronzite gedritites occur in the Central Province of Zambia. Experimental work in the system MgO-Al2O3-SiO2-H2O suggests that these assemblages formed at pressures in excess of 10 kb.

New analyses are given of granites from 23 intrusions in Scotland, Ireland, and the Isle of Man. Together with existing analyses, these were used to measure the regional variation in composition of Caledonian granites by means of trend surface analysis. An explanation of the variation is presented that involves the production of magma by melting in the crust, at a depth determined by the geothermal gradient.

The cell dimensions of powder samples of some Bushveld titanomagnetites and ilmenites were determined using a 114·6 mm AEG Guinier camera. The average cell dimension of the titanomagnetite is 8·400±0·005 Å and there is no definite relationship between the cell edge of the samples and their position in the layered sequence. The average cell parameters of coarse-grained ilmenite are a 5·085±0·005 Å and c 14·09±0·02 Å. Ilmenite that has replaced ulvöspinel has on average a value of some 0·003 Å greater than that of associated coarse ilmenite grains.

Chemical analyses indicate that titanomagnetite from pegmatoidal plugs and from the top of layered sequence was generally subject to late-stage magmatic alteration and hence lies in the Titanomagnetite II field. In the Bushveld Complex there is an increase in the TiO2 content of titanomagnetite from some 12 % at the base to 18 % at the top of the Upper Zone. However, Bushveld titanomagnetite tends to be poorer in TiO2 than similar samples from the Skaergaard intrusion.

A discrepancy between modal and normative hercynite in the Bushveld samples indicates that a considerable amount of hercynite is probably still in solid solution in the titanomagnetite.

Chemical analyses of Bushveld ilmenites reveal that they lie in the same tholeiitic field as those of the Skaergaard intrusion.

A minor phase in iron-ore sinters has been synthesized and identified as a clinopyroxene with the approximate formula Ca1·0(Ca0·14Al0·60Si1·08)O6. This composition shows that it consists largely of the hypothetical Tschermak's molecule, M2+SiO6. The small size and sparse distribution of this phase in most iron-ore sinters has previously hindered analysis.

To produce a lattice expansion readily detectable by conventional X-ray photographic means in α-irradiated diamond, a dose of order 1018α.cm−2 is required. Such a dose could be produced by pitchblende in ∼2 × 108 yr. and a previously reported lattice expansion in a natural diamond could therefore have occurred by long-term contact with a radioactive material. α-particle doses greater than ∼1014 cm−2 produce observable green colouration on the surface of an initially colourless diamond.

Examination of published procedures for the decomposition and subsequent analysis of chromite and chrome ores shows some to be unnecessarily complicated and time consuming. Others fail to yield consistent and reproducible results. Decomposition is rapidly and effectively accomplished using the peroxide frit technique of Rafter. Chromium may then be removed and determined volumetrically allowing the rest of the analysis to proceed along conventional silicate lines. Fe2+ is determined by oxidimetry following digestion with a mixture of phosphoric and sulphuric acids in the presence of ceric sulphate.

Coexisting hornblende and cummingtonite in an amphibolite near Peliwali have been analysed. The rock formed by Fe-Mg addition and Ca removal from pre-existing amphibole quartzites within the altered wall rocks surrounding sulphide lodes. The amphibole compositions are controlled by the bulk composition of the rock. The Mg/(Mg+Fe2+) ratio of the hornblende (0·66) is only slightly higher than that of the cummingtonite (0·64).