Anandite is a new barium iron silicate found in the magnetite ore zone of the Wilagedera iron ore body, in the North Western Province of Ceylon. The mineral is named after the late Dr. Ananda Coomaraswamy, the first director of the Mineral Survey of Ceylon.

Anandite is monoclinic, with a 5·412, b 9·434, c 19·953 Å, β 94° 52′, space group C2/c. D 3·94, hardness 3–4. Optically positive, b ‖ β, γ ∧ a 12°, β 1·855, γ > 1·88. Pleochroism: β green, γ brown. Chemical composition corresponds to the simplified formula (Ba,K) (Fe,Mg)a (Si,Al,Fe)4O10 (O,OH)2 with Z = 2. The data available indicate that the mineral has the trioctahedral structure of the brittle micas.

Chemical analyses, some optical data, and specific gravities are given for 57 pyroxenes from the alkaline rocks of Uganda. They are members of the diopside-hedenbergite-acmite series, the more diopsidic varieties occurring in rocks of the ijolite series and the more acmitic in syenites and carbonatites. TiO2 is highest in those pyroxenes from rocks that do not contain melanite. The refractive indices and specific gravities are controlled by the Fe2+/Mg ratio in the diopsidic pyroxenes and by the Fe3+ content in the acmitic members. Paragenesis is discussed briefly.

In the south-eastern part of the Khetri copper belt, actinolite occurs in association with alteration assemblages resulting from the Fe-Mg metasomatism that accompanied sulphide mineralization, and more commonly with albite-bearing rocks formed by albitization of quartzites and schists near granitic rocks. Within the latter occur many coarse, massive, and unoriented aggregates of actinolite crystals, individuals being commonly more than 10 cm long. Locally fluorite-bearing veins oecur within granitic and albite-quartz rocks. The actinolite is pleochroic from pale pink to green; γ: [001] = 26°; γ = 1·642 ± 0·003; 2Vα = 80°. The composition of the analysed actinolite closely compares with those published in the literature excepting in (OH), which is low. The mineral assemblages, formed by metasomatic replacement of pre-existing rocks, are equivalent to those of albite-epidote-amphibolite facies. The metasomatic fluid was apparently rich in Ca, F (indicated by fluorite), and oxygen (indicated by magnetite, ilmenite, and hematite).

A hypothesis for the mechanism of oxidation in titanomagnetites is first put forward on the basis of new oxidation data for pure magnetite and the new model for cation distribution in titanomagnetites. Contrary to previous claims by other workers, it is shown that single-phase spinel oxidation products of titanomagnetites can only be produced under very exacting circumstances. Lowtemperature magnetic measurements on such synthetic, oxidized materials were made to show the formation of magnetite by the decomposition of the metastable oxidation products of titanomagnetites on prolonged heating at moderate (∼ 390° C) temperatures. This magnetic method of detection is more sensitive than that of normal X-ray diffraction. It is concluded that previous claims of an increase in magnetization due to the formation of synthetic single-phase, highly oxidized titanomagnetites must be due to the formation of undetected magnetite.

Gersdorffite belongs to space group P213 in the cubic system with cell dimension a 5·6885 ± 0·0003 Å and four formula units per cell. The hk0 data were measured from precession photographs obtained with Mo-Kα radiation. The structure was solved by Patterson methods and refined by least-squares techniques. This structure has complete ordering of arsenic and sulphur similar to ullmannite.

Members of the KAlSi3O8-BaAl2Si2O8 feldspar series have been synthesized by hydrothermal methods. Although the products are too finely crystalline for complete detailed study, some X-ray and optical measurements have been made, together with some electron-diffraction observations.

The results presented confirm the existence of high structural states over the greater part of the series, and suggest that a simple solid-solution series is formed between the end-members at high temperatures.

In the rich mineral assemblage found in the pegmatites of Rhodesia and Uganda are members of the amblygonite-montebrasite series with α 1·592–1·615, γ, 1·612–1·638, the highest values corresponding to montebrasite, Li1·98Al2·00 (P1·95O7·90)(OH1·90F0·20); apatite with up to 8·8 per cent MnO; heterosite (new analysis) and other manganese-iron phosphates; and a variety of niobium-tantalum and uranium minerals.

A zinc-rich helvine (genthelvite) has been found with bertrandite in miarolitic cavities in adamellite at Coire an Lochain in the Cairngorm Mountains. The genthelvite occurs as green or brown tetrahedral crystals of sp. gr 3·58±0·01. It is isotropic, n 1·742±0·003, a 8·133±0·005 Å. Bertrandite crystals are pale brown with sp. gr. 2·60±0·01; biaxial negative with 2V 75°, and α 1·590, β 1·603, γ 1·613, all ±0·003.

A heulandite from Nelson Creek, Skamania County, Washington, has 30 H2O per unit cell instead of the normal 24; the excess water is lost on gentle heating. The b and c cell-dimensions are also rather larger than normal. Normal heulandite also occurs in the same area.

Fibres of hematite in kidney ore are elongated at right angles to the c-axis. The fibre axis, which may be normal to a face of either of the hexagonal prisms {101̄0} or {112̄0}, may show an abrupt change of orientation along the length of a fibre. There is little preferred orientation around the length of the fibres.

It is confirmed that in some calcite satin spar the fibres are elongated parallel to an edge of the cleavage rhombohedron; in other fibrous growths the elongation is either parallel to or Perpendicular to c.

Attempts to reproduce the X-ray measurements which led W. L. Brown to postulate the existence of monalbite at room temperature were unsuccessful.

A neutron activation analysis of one of the crystals of ‘monalbite’, which was monoclinic at room temperature, shows that it contains a large proportion of potassium. It is thus not a polymorph of pure NaAlSi3O8. The contamination occurred by transfer of K through the atmosphere of the furnace from potassium-bearing ceramic materials.

Measurements from powder diffraction patterns recorded at temperatures up to 950° C for the supposed equilibrium forms of albite synthesized at 800°, 900°, and 1000° C by MacKenzie (1957) indicate that only the form synthesized at 1000° C becomes monoclinic. Single-crystal measurements on heated pure natural albite (Ab99·26) show that it becomes truly monoclinic, both in geometry and intensity distribution, at 930° C, the same temperature as for the highest-temperature synthetic form. These experiments were carried out in conditions that exclude possible contamination by potassium.

Garnets undergo readjustment of ion-assemblages under external mechanical and thermal stresses; this adjustment favours those paths that annul the very cause to which it is due. Metal ions in garnets being replaceable, with rising metamorphism garnets become reluctant to accommodate ions of larger ionic radii.

Data from recent literature on chemical analyses of garnets from rocks belonging to different grades of regional metamorphism reveal that the (FeO + MgO) content of garnet varies linearly with (CaO + MnO) content. As the Fe/Mg ratio does not vary appreciably, a fair estimate of metamorphic grade can be made from a knowledge of (CaO + MnO) or of (FeO +MgO) individually or even, with less confidence, of FeO or MgO alone. From the study of the available data it is found that (CaO + MnO) and (FeO + MgO)/(CaO + MnO) provide the best indicators of progressive metamorphism. Cell edges of garnets decrease progressively with increasing metamorphism and this may also be used as a fairly good index of metamorphism. When cell edges are plotted against (FeO + MgO)/(CaO + MnO), a hyperbolic curve is obtained.

A rapid method for determining the mode of a four-component powder (microcline, orthoclase, plagioclase, and quartz) was sought to aid the interpretation of geochemical results. An accuracy of about ±5 % (absolute) was required. Three methods were tried : point counting proved too long as well as destroying the sample; infra-red spectroscopy was not sufficiently accurate for this particular type of rock powder; X-ray diffraction proved the most rapid and, although less accurate than point counting, was within acceptable limits and had the advantage of giving additional information about the composition of the feldspars.

Pure dry chlorine at 250 to 350° C is shown to have no action on the principal silicate and phosphate phases of meteorites, but reacts quantitatively with the sulphide and phosphide phases and with kamacite; taenite does not react if it contains more than about 20 to 25 % Ni; some rare meteoritic minerals have not yet been tested. Volatile chlorides (including SiCl4) distil, and non-volatile chlorides can be leached out with water. Based on these observations, a method has been devised and applied to the analysis of a number of chondrites and to the purification of olivine and pyroxene separated by physical methods. The amount of Si present in the metal of enstatite chondrites, and the distribution of P, Ga, Ge, Ti, Cr, Mn, Ca, and Mg between oxidized and non-oxidized phases can readily be determined, and some results are presented. From the limited data so far available, Co appears to be concentrated in kamacite; gallium in the metallic phase is mainly in the taenite; germanium is strongly siderophile in the common chondrites but some is present in the silicate of the enstatite chondrites; titanium is markedly chalcophile in the enstatite chondrites, less so in the common chondrites, and the same applies to chromium; phosphorus is present as phosphide in the enstatite chondrites, but as phosphate in the hypersthene chondrites.

The Woodbine meteorite, ploughed up in Illinois in 1953, is a fine octahedrite with numerous inclusions of silicate minerals. The minerals present include kamacite, taenite, troilite, schreibersite, orthopyroxene (Fs6), diopside, olivine (Fa4), plagioclase (An9), and graphite. The chemical analysis is: Fe 73·06, Ni 9·08, Co 0·15, P 0·47, C 0·21, FeS 1·65, SiO2 8·55, TiO2 0·02, Al2O3 0·53, Cr2O3 0·03, FeO 0·49, MnO 0·03, MgO 5·19, CaO 0·34, Na2O 0·29, K2O 0·02, sum 100·11. Woodbine is compared with other meteorites of similar composition. The silicate material has chondritic composition, and is quite different from the silicate material of the mesosiderites, with which some of these meteorites have been classed.

A modification of the one-axis spindle-stage for the study of the optical indicatrix of crystal grains on the polarizing microscope is described. It allows the crystal to be rotated around axes within a range of about 40° without having to remount it. Some advantages of this variable-axis spindle-stage for obtaining extinction curves and equivibration curves (n0 curves) are illustrated.