Bideauxite is a new mineral found in specimens from the Mammoth-St. Anthony mine, Pinal County, Arizona. The composition is Pb2AgCl3(F,OH)2 with Pb, Ag, Cl, F by duplicate wet analyses. Z = 16, G. calc. 6·256, meas. 6·274 (at 24·2 °C). Crystals are isometric hexoctahedral with a 14·132 Å. Space group Fd3m. Crystals show a, o, d, m {113}, μ {114}, n {112}, φ {116}, and {029} in decreasing order of importance. Colourless, transparent with white streak. Isotropic with nD 2·192. le, almost sectile, withc onchoidal fracture. H = 3. Turns pale lavender in strong light. Low M.P. B.P. Decomposes in acids and warm NH4OH. Bideauxite is an oxide zone mineral found with leadhillite, matlockite, and anglesite. May alter to cerussite.

Hodrushite, a new sulphosalt of copper and bismuth, was found in the Rosalia ore vein at Banská Hodrušá near Banská Štiavnica, Czechoslovakia. It has chemical composition Cu8·12Bi11·54Fe0·29S22 (as determined by electron-microprobe method) close to Cu8Bi12S22. Symmetry is monoclinic, space group A2/m, lattice constants a 27·21, b 3·93, c 17·58 Å, β 92° 9′, measured density 6·35, calculated density 6·45 g/cm3. Microhardness 200 kg/mm2, anisotropic, weak bireflectance, creamy with pinkish tint, maximum reflectivity about 6000 Å. Crystals needle-shaped and striated along [010], colour steel-grey, quickly tarnishing to bronze. Associated with quartz, hematite, and chalcopyrite. Closely related to cuprobismutite.

Chemical, optical, and X-ray data are presented for pyroxenes from a representative selection of chondrites. The Mg-Fe pyroxenes originally crystallized above 1000-1200 °C as the protoenstatite-protohypersthene polymorph, and inverted on cooling to the polysynthetically twinned clinoenstatite-clinohypersthene polymorph. In most chondrites the latter became converted to orthopyroxene during recrystallization at temperatures ranging up to 900 to 950 °C. The contents of certain minor elements changed during the clino-ortho inversion. Ancestral protoenstatiteprotohypersthene may have been slightly non-stoichiometric. Accessory Ca-rich pyroxenes are discussed briefly.

The kamacite contains a general precipitation of micrometre-sized particles of exsolved taenite. Larger particles are found decorating Neumann lines and at kamacite grain boundaries. The coexisting kamacite and taenite appear to have nickel contents of 6·4 % and about 53%, which are consistent with a temperature of about 330–60 °C on the binary iron-nickel equilibrium diagram.

A review is given of the metallurgical literature relating to the formation of metal rodeutectics, which are texturally similar to myrmekite. Since no satisfactory explanation for rodeutectics has been advanced, a comparison is made with myrmekite. It is proposed that this intergrowth develops as a result of the constriction of quartz during its recrystallization and inclusion in an expanding blastic growth of plagioclase, and the forces involved lead to the prolongation along the growth directions of quartz in the form of rods with a relatively small surface area (i.e. with circular cross-sections). Possible forces that could produce the same geometry in metal intergrowths are those that result from the relative contractions of the two components during freezing; in all cases for which quantitative data are known, the metallic rods have a greater contraction on freezing than the host substance. Examples of myrmekite and myrmekite-like intergrowths in the Constant Gneiss are described in relation to their particular origin. Two factors, the lack of proportionality of qtartz to feldspar and the intimate association of myrmekite with myrmekite-like intergrowths, support the proposed mechanism of constriction of pre-existing quartz.

Chemical analyses and optical properties of ten orthopyroxenes, two clinopyroxenes, and six biotites (partial analyses) are presented from basic to intermediate charnockites of the Garbham area. The orthopyroxene is hypersthene to ferrohypersthene and the clinopyroxene is sahlite. Biotite has secondarily formed from pyroxene, particularly orthopyroxene, as a result of injection of potassic fluid in the basic charnockite. By combining the data of Srikakulam with those from other areas of the world it is shown that during the transformation of pyroxene to biotite in charnockitic rocks, in general, Mg and Fe 2+ attain near-equilibrium distribution between orthopyroxene and biotite as well as between clinopyroxene and biotite. The magnesium distribution coefficient (KD) of coexisting orthopyroxene and biotite is found to increase with the increase of temperature of biotite formation. A tentative geothermometric scale has been proposed plotting temperature of biotite formation against magnesium distribution coefficient of coexisting orthopyroxene and biotite. According to this scale, biotite in basic and semibasic charnockites from Garbham has formed between 285 and 465 °C.

The occurrence of coexisting paragonite (containing 0·70 % CaO) and muscovite (containing 0·16 % CaO) in a staurolite-grade paragonite-muscovite-hornblende-garnet-biotite schist from Sulitjelma enables an estimate to be made of the temperature of recrystallization, using an extension, based on crystal chemistry considerations and available analyses of muscovites and paragonites from metamorphic rocks, of the experimentally determined solvus in the K-Na white mica system into the Ca-K-Na system. This temperature of recrystallization is approximately 550–70 °C and is consistent with the experimental data on the coexistence of staurolite and quartz in the system Fe-A1-Si-O-H (Richardson, 1968).

Russellite Bi2O3. WO3 occurs in a small pegmatite near Poona, Western Australia. The fine-grained yellow to pale green material is an inseparable mixture of russellite, bismite, koechlinite, and bismutite. X-ray powder diffraction, physical, and chemical data agree in general with the original description of the mineral from Cornwall, England. The original analyses made on micro quantities are now supplemented by analyses on macro quantities.

The manganiferous amphibole juddite has been reported by a number of workers from metamorphosed manganese formations of India. The mineral is developed at the contact of pegmatite and gondite, and associated characteristically with blanfordite (manganoan aegirine-augite) and winchite (manganoan richterite-tremolite). The range of the refractive indices of the mineral and the orientation of the optic axial plane normal to (010) suggest the mineral to be of magnesioriebeckite composition. The 100 Mn2+:(Mn2++Mg+Fe2+) and 100 Fe3+:(Fe3++Alvi+Ti) ratios plotted in the glaucophane-magnesioriebeckite diagram show that eight out of nine analyses (eight new) are grouped under magnesioriebeckite composition range. It may thus be concluded that the juddites generally refer to (manganoan) magnesioriebeckite compositions. In some cases, however, the composition of juddite shows considerable departure from ideal magnesioriebeckite composition and the juddite and winchite (manganoan tremolite-richterite) show evidences of compositional transition, indicating partial miscibility. The juddites have been formed by the interaction of pegmatitic fluid on manganese ore, gondite, and other country rocks such as mica schists and diopside-forsterite marble.

Chemical analyses, optical properties, specific gravities, and cell dimensions are presented for six topazes. A linear relationship is confirmed between the b cell dimension and the OH/(OH+F) ratio.

Petrographic descriptions, bulk chemistry, and partial analyses of several mineral phases in each stone are presented. Medanitos, previously classed as a eucrite, is now shown to be a howardite: Putinga is an equilibrated olivine-hypersthene chondrite.