Parahopeite, Zn3(PO4)2.4H2O, is the triclinic dimorph of hopeite. The crystal structure of parahopeite has been determined to be similar to phosphophyllite, Zn2Fe(PO4)2.4H2O and to hopeite in that one of the two zinc atoms is six-coordinated and the other is four-coordinated. Parahopeite differs from the other two minerals though because one of the P-O tetrahedral oxygen atoms is bonded to both the six- and the four-coordinated cations. That is, all four tetrahedral oxygen atoms are bonded to the four-coordinated zinc in parahopeite, whereas in phosphophyllite and hopeite only three of these oxygen atoms are so bonded.

Evidence of preferential crystal growth along tilt and twist boundaries was observed on a hematite crystal from St. Gothard, Switzerland. Irregular lines that cut across the triangular growth layers on the (0001) face develop around a misoriented hematite crystal. There is a slight inclination of the surface on both sides of the lines, suggesting that they are small-angle grain boundaries (tilt and twist boundaries), consisting of screw and edge dislocations. Both spirals and triangular terraces occur along these lines, in addition to the original triangular growth layers. Growth spirals are also present on the (101̄1) faces, distributed along certain lines. From these observations it is concluded that preferential crystal growth took place, during the final stage of growth of the host crystal, at both screw and edge dislocations in the tilt and twist boundaries. The latter were formed by the impinging of another hematite crystal on the growing surface of the host crystal.

The observed order of importance of the forms of cerussite has been determined by the methods introduced by Donnay and Harker, used in a modified form. The space group derived by morphological analysis is Pmcn, as determined by X-ray diffraction. For the more common forms good agreement is found between the observed and theoretical orders of importance. The rank distribution of the more important forms is given.

The classification of framework structures built from chains of four-membered rings of type UUDD is incomplete: there are two basic ways in which the chains can be cross-linked to form eight-membered rings. The first type of frame-work (already described) is extremely flexible, permitting the cavities to be either large or small; the second type is inflexible and the cavities are small. Feldspar belongs to the second type and had been incorrectly ascribed to the first type: paracelsian, harmotome, and gismondine had been correctly placed in the first group.

Oxides of the Cu-Fe-O system prepared by solid-state reaction methods have been investigated by X-ray, Mössbauer effect, and analytical chemical techniques. In agreement with most previous investigations of this system, it is found that CuFeO2 exists as a stable compound, and that the mineral delafossite has essentially this composition. These results are in disagreement with those of Buist, Gadalla, and White who propose that delafossite has an approximate composition Cu6Fe3O7 instead of CuFeO2. In fact, a compound of composition Cu6F3O7 could not be prepared. The Mössbauer isomer shift provides confirmation that the iron in CuFeO2 is trivalent.

Two new microanalyses of delafossite from Nizhniĭ Tagil (the type locality) and Kimberly, Nevada, confirm the accepted formula CuFeO2.

The compositions of more than eighty synthetic members of the apatite group with the general formula A10(XO4)6Z2 have been used as a basis for classifying the apatites into three groups. The ratios of the mean sizes of the ‘A’ ions to those of the ‘X’ ions for all these compositions lie between the limits of 1·89 and 4·43. A discontinuity occurs between ratios of 2·50 and 2·60 and probably another between 3·25 and 3·35, and these discontinuities provide a structural basis for the division into the three groups. The groups are named after well-known mineral species occurring in each group, i.e. the vanadinite-svabites with an A : X ratio less than 2·5, the apatite-mimetites between 2·60 and 3·25, and the pyromorphites with A : X greater than 3·25.

The distribution of trace elements is studied in different acid and basic rocks, adjacent to the copper lodes in the Mosaboni mines, Singhbhum, and adjoining the thrust zone, as well as of areas far away from the mineralized zones. Specific differences in composition and trace constituents in these rocks especially as regards S, Cu, Ni, and Co, suggest that the relationship of the Singhbhum granite with the soda granite is most unlikely, and that there is a connection between the soda granite and the sulphide ore-fluid ; a genetic relationship of sulphide mineralization with the epidiorite is doubtful. The possibility of the existence of a common source for the Chotanagpur granite and the Singhbhum granite is inferred.

The minor elements present in some rocks and minerals of the Rakha mines area, Singhbhum district, Bihar, India, have been determined by X-ray fluorescence spectroscopy. Geological and geochemical studies in different parts of this shear zone already favour a hydrothermal origin. Some of the minor elements concentrated in the sulphide ores are found in lower concentration in the epidiorite and the chlorite-mica schist; these are, however, present in abundance in the soda-granites that are closely associated in space to the east and west of the Rakha mines area. A genetic link between sulphide ores and soda-granite may be predicted although the sulphides in the Rakha mines area are not directly associated with the soda-granite.

Calcium hexaluminate has recently been confirmed as a stable phase occurring within the system CaO-Al2O3. In the present investigation, this aluminate has been synthesized from the constituent oxides and its X-ray, optical, and physical (microhardness and reflectivity) properties determined. Similar data have also been obtained on the ferrian phase from the immediate hot-face zone of high-alumina bricks that had been in service in electric arc furnace roofs. An electron-probe microanalysis study revealed that between 12 and 13 % atomic replacement of Al by Fe had occurred in this ferrian calcium hexaluminate. The melting behaviour of the pure compound has been studied by firing pellets in a specially-constructed vacuum furnace. Results show the incongruent melting point to be 1870°C (±10° C), while the liquidus temperature is 1970° C (±10° C). These points were determined by examining polished sections of compacts heated within the range 1820 to 2000° C. A revised phase diagram of the high-alumina portion of the system CaO-Al2O2 is presented.

From a metallographic study the thermo-mechanical history of Kodaikanal is proposed as a slow structure-forming cool, followed by mechanical damage, then mild reheating, and finally entry to earth.

Two groups of meteorite finds in separate areas of the Nullarbor Plain are reported. It is suggested that the grouping is due to the fact that these are areas in which a family of rabbit trappers operates: these people have made most of the finds. There is, however, one shower of 71 small meteorites represented. Several arrivals on earth are represented by each group. The meteorites are described and it is shown that several distinct types are represented. Two quite different ureilites have been identified—only the fourth and fifth ever discovered in the world. Analyses are given for these rare carbonaceous achondrite meteorites. The remainder of the stones are olivine-hypersthene and olivine-bronzite chondrites. The whole question of the reason for the profusion of meteorite recoveries now being made on the Nullarbor Plain is briefly discussed.

These minerals indicate strongly reducing conditions as well as extremely low sulphur fugacities within the Newport pallasite. They all formed at low temperatures (upper limit 580° C) and in the solid state. This is the first reported occurrence of mackinawite and pentlandite from a pallasitic meteorite; Cu is known from only one other pallasite. Microprobe analyses of a large Cu grain indicate its composition as 98·6 ± 0·5 %, Ni 2·0 ± 0·5, Fe below the limit of detection (∼0.3).

The Bencubbin meteorite and some of its enclaves have been studied in thin section under transmitted light: supporting X-ray diffraction and chemical data have been supplied by the Smithsonian Institution, Washington. These results show the host material to consist of clinoenstatite and a little olivine (both nearly pure magnesian varieties) set in an opaque (cryptocrystalline ?) base, which is, in turn, enclosed in a mesh-work of nickel-iron, of composition equivalent to a hexa-hedrite. Two enclaves are revealed as: an atypical olivine-hypersthene chondrite (in the mode, the olivine is Fa19, and pigeonite takes the place of orthopyroxene, but the chemical analysis is typical except for a small but appreciable carbon content); and an enstatite chondrite displaying crudely formed chondrules (chemically typical, with a small but appreciable carbon content).

The chondrite enclaves are not recrystallized: though Lovering has referred to the first as ‘thermally metamorphosed’, and both are dark coloured, there seems to be little evidence of the effect of the metallic host, which must surely have been molten, on the chondrite enclaves, which seem to have been able to survive in this environment without mineralogical or textural modification.

Lovering has stressed the importance of this meteorite in its bearing on meteorite provenance and genesis, and the further implications of this present study are discussed briefly.