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.

Onoratoite, a new antimony oxychloride Sb8O11Cl2 from the antimony mines of Cetine di Cotorniano, Rosia (Siena, Italy), is triclinic with lattice constants a 18·92, b 4·03, c 10·31 Å, α ≃ γ ≃ 90°, β 110°. Density 5·3 meas., 5·49 calc. The needle-like crystals are elongated on [010] and show as prominent form {001}. Other forms present are {100}, {201}, {401}, {412}.

The new mineral is optically biaxial negative, extinction angle small and variable from 0° to 14°. Orientation β:[100] ca. 8°; α:[001] ca. 12°; γ:[010] 0 to 14°. Refractive indices are 2·26 > γ > 2·23, 2·23 > β > 2·18. Birefringence γ-β 0·024 (meas.).

The stability field of onoratoite has been investigated by systematic thermo-gravimetric and differential thermal analysis of antimony oxychlorides and by a direct study of equilibrium relationships in the system SbCl3-Sb2O3-HCl-H2O. The probable mechanism of formation of onoratoite is discussed.

Onoratoite is named in honour of the Italian mineralogist Ettore Onorato.

The chemical analyses, structural formulae, and trace element data are presented for 18 orthopyroxenes and 9 clinopyroxenes from the charnockitie rocks of Kondapalli, Andhra Pradesh, India. The chemistry of these pyroxenes is discussed and conclusions are drawn. The data are compared with the similar data available for the pyroxenes of the charnockites of the type area near Madras, some 200 miles south of Kondapalli. The element-distributional relationships between the coexisting pyroxenes are discussed and inferences are made regarding the temperature of crystallization of charnockite pyroxenes.

The petrography of the Mount Padbury meteorite, previously briefly recorded, is described in some detail. Both the metalliferous host material of the mesosiderite and the varied range of silicate-rich, virtually metal-free enclaves (including both familiar achondrite material and unfamiliar achondrite material) are described. Eucrite, brecciated eucrite, and a peculiar ‘shocked’ form of eucrite (resembling some terrestrial flaser-gabbros) are the calcium-rich achondrite types represented; hypersthene achondrite (including typical diogenite material and unfamiliar material) and olivine achondrite (granular aggregates of olivine not entirely similar to the unique chassignite and single crystals up to 4 in. in length) are the calcium-poor achondrite types represented. The eucrite displays more or less uniform mineralogy, but the mineral constituents are present in varying proportions, and there is a wide range of textural variations recognized. The silicate grain fragments enclosed in the metallic reticulation to form the mesosiderite host material are, significantly, entirely of minerals seen within the achondrite enclaves—plagioclase, hypersthene, pigeonite, olivine, and tridymite.

These results include microscopic analysis of thin sections and polished sections, X-ray diffraction studies, optical determination of refractive indices using mineral grain mounts, and chemical analyses.

The wider implications of this new and unique meteorite find are briefly considered.

Chemical and single crystal X-ray studies have shown the existence of a 9-layer polytype of taaffeite. The parameters of the hexagonal unit-cell are a 5·675 Å, c 41·096 Å (arh 14·085 Å, α 23·24°). The oxide composition of the mineral is Al2O3 71·44, MgO 15·76, FeO 6·78, BeO 5·50%. It is pale olive green, with refractive indices ω = 1·739, ε = 1·735, and a specific gravity of 3·68.

Two monoclinic minerals formerly classified as ganophyllite have been differentiated on the basis of single-crystal X-ray data. True ganophyllite occurs at the Harstig mine, Pajsberg, Sweden (a, 16·60 ± 0·05 Å; b, 27·04 ± 0·08 Å; c, 50·34 ± 0·15 Å; β, 94° 10′ ± 10′; space group A 2/a), at the Benallt mine, Caernarvonshire, Wales, and in Aroostook County, Maine. Bannisterite, a new mineral, occurs at Franklin, New Jersey (a, 22·20 ± 0·07 Å; b, 16·32 ± 0·05 Å; c, 24·70 ± 0·08 Å; β, 94° 20′ ± 10′; space group A2/a) and at the Benallt mine, Wales. Both minerals have similar pseudocells: a, 5·53 Å; b, 3·3 Å; c, 25 Å; β, 94° The chemical analysis of ganophyllite from the Harstig mine, Sweden, is: SiO2, 39·67 %; Al2O3, 7·95; Fe2O3, 0·90; MnO, 35·15; CaO, 1·11; MgO, 0·20; PbO, 0·20; K2O, 2·70; Na2O, 2·18; Li2O, trace; H2O, 9·79; total, 99·85. The chemical analysis of bannisterite from Franklin Furnace, New Jersey, is: SiO2 46·20 %; Al2O3, 4·74; MnO, 23·02; FeO, 6·40; ZnO, 4·67; CaO, 1·52; MgO, 1·99; Na2O, 0·29; K2O, 1·21; H2O, 9·74; total, 99·78.

Both ganophyllite and bannisterite show a structural resemblance to stilpnome-lane from Deer Isle, Maine, in projection on selected zones. All three have a micaceous cleavage parallel to {001} in the orientations here taken. Stilpnomelane is triclinic, pseudotrigonal, and pseudomonoclinic. In the triclinic cell, a = b, 22·05 Å ± 0·06 Å; c, 17·70 ±0·06; α, 124° 49′; β, 95° 58′; γ, 120° 00′ (angles ± 5′). In the trigonal subcell, a′, 3·2 Å; c′, 36·4. Small distorted trigonal subcells for ganophyllite have a′, 3·38 Å; c′ 37·7, and for bannisterite have a′, 3·264 and c′, 37 Å.

An occurrence of todorokite having a formula is recorded from Ardglen, 150 miles N.N.W. of Sydney, New South Wales. The composition of Ardglen todorokite is somewhat simpler than previously recorded occurrences, most of which were in manganese and manganese—base-metal ore deposits. The simpler composition is explained in terms of its occurrence as a late deuteric mineral associated with manganocalcite and zeolites in an altered Tertiary basalt. The manganese is believed to have been derived from the deuteric alteration of the augite of the basalt.

The crystal structures of sjögrenite and pyroaurite, two stacking modifications of approximate composition Mg6Fe2(OH)16(CO3).4H2O, have been determined by X-ray diffraction using three-dimensional methods. Sjögrenite is hexagonal, with a 3·13, c 15·66 Å, space group P63/mmc , Z = ¼; pyroaurite is rhombohedral, with aH 3·13, cH 23·49 Å, space group R3̄m or R3m, Z = ⅜. Both structures are based on brucite-like layers, with magnesium and iron distributed among the octahedral positions. The cations appear to be largely disordered, although ordered regions may occur in some crystals. Between the brucite-like layers are the water molecules and carbonate groups. These are statistically arranged, with their oxygen atoms distributed among a larger number of possible sites.

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.

The crystal structure of epistilbite ((Ca2·59Na1·06K0·10) (Al6·29Si17·71O48).15·74H2O; C2/m; a = 9·08, b = 17·74, c = 10·25±0·01 Å; β = 124·54±0·05°) was determined by 3-D least-squares methods. The alumino-silicate framework is composed of 4-, 5-, and 8-membered rings of tetrahedra. There are two sets of intersecting channels each defined by 8-membered rings. The (Ca, Na) atoms in the channels are in contact with seven water molecules and two oxygen atoms giving a coordination of nine at a cut-off distance of 2·77 Å. The average tetrahedral distance is lower than for anhydrous framework alumino-silicates but consistent with some other zeolite structures. Partial Al-Si ordering exists with one tetrahedron occupied preferentially by aluminum. This tetrahedron contains the two oxygen atoms that are coordinated with the (Ca, Na) atom.

There is an important corollary to Prior's rule to the effect that as the state of oxidation of meteorites is increased the quantity of olivine increases relative to pyroxene and metallic iron. We have derived a rigorous parametric expression for this corollary and find that, as in the case of the quantitative interpretation of the rule itself, there is in this case also a fair correspondence to the observational data, so that the validity of the rule is further supported.

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.

Despite a wide range in parent rock compositions, from analcime-olivine theralite to analcime-tinguaite, clinopyroxene phenocrysts in the Square Top intrusion show limited compositional variation. The crystallization trend of the pyroxenes (principally sahlites) lies approximately parallel to the diopside-hedenbergite join of the pyroxene quadrilateral, and in addition reveals slight enrichment in acmite. The limited iron enrichment in the pyroxenes (and in olivine phenocrysts in the theralites and tinguaites) stemmed from progressively more hydrous liquid fractions whose ferric/ferrous iron ratios increased during differentiation.

Further data are presented on the properties of natural and synthetic members of this series. Cell constants have been determined for over 50 specimens across the composition range; the activation energy for a low-high transformation in an intermediate hyalophane has been evaluated as 101·5 ± 5·0 kcal/mole; additional single crystal studies have revealed complexities not previously reported.

Although there remain many detailed problems to be resolved, the present studies allow some suggestions concerning the nature of the relationships within the series. Problems of nomenclature and subsolidus relations are discussed together with some structural implications.

Thermal expansion data up to 920° C by powder X-ray diffraction methods are presented for four noseans, five haüynes, and one sodalite. The rate of thermal expansion is at first high and increases with temperature; this is interpreted as due to the untwisting of the partially collapsed framework. Above a certain temperature (which depends on the mineral and its composition) the rate of thermal expansion is much lower and is linear with temperature; this corresponds to the rate of thermal expansion of the more fully expanded framework. Sodalite does not show this second stage below 920° C. The thermal expansion behaviour of other framework silicates is interpreted in analogy to that of the sodalite group.

Quantitative electronprobe microanalyses have been made of stannite from various localities. It was found that in general this mineral corresponds in composition to the formula Cu2FeSnS4. However, noticeable deviations in the ratio of the metals can occur and considerable concentrations of zinc may be present.

Some tin minerals related to stannite have also been analysed, namely hexastannite, mawsonite, and an apparently hitherto unknown mineral to which the name rhodostannite is given.

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.

Chemical data are presented for four hypersthenes and one coexisting hypersthene-augite pair, and chemical, X-ray, and thermomagnetic data presented for five titaniferous magnetites, all from various horizons of the Taupo pumice sequence. These phenocrysts are regarded as primary crystallization products, and not of xenocrystic origin. The hypersthenes range from Mg46·4Fe51·4Ca2·2 to Mg65·7Fe31·2Ca3·1; the augite composition is Mg48·5Fe12·3Ca39·2. The occurrence of such magnesian pyroxenes may be explained by the early separation of titaniferous magnetite, although it is also possible that the initial iron ratios of the liquids were already sufficiently low to precipitate these pyroxenes.

The magnetites exhibit varying stages of oxidation. Data on the least oxidized specimens indicate they were initially magnetite-ulvöspinel solid solutions, with 40 to 50% (mol.) solid solution ulvöspinel. Subsequent oxidation has modified their compositions; there is some evidence that this could have occurred during normal weathering processes.

Calzirtite, essentially CaTiZr3O9, has been identified in residual soils from the Bukusu carbonatite complex in Uganda. A satisfactory ultrasonic technique was developed for cleaning the samples prior to studying their mineralogy. Other heavy minerals present include ilmenite, perovskite, melanite, apatite, zircon, and baddeleyite. The properties and composition of calzirtite are compared with the available data from occurrences in the U.S.S.R. The mineral has a metasomatic paragenesis and probably indicates the presence of carbonatized rocks at depth.

Properties and possible structures of hydronium trihydrate H9O+4 and hexahydrate H15O+7 are considered. From the 2330 minerals listed in Strunz's mineralogical tables nineteen were selected that appear to contain H+.4H2O or H+.7H2O, and the possibility of discrete H9O+4 or H15O+7 groupings existing in their crystal lattice is discussed. From a crystallochemical point of view the most probable examples of hydronium hydrate compounds are layer lattice minerals like H-montmorillonite, H-vermiculite, troegerite, H-meta-autunite, sabugalite, and hewettite.