A simple method has been developed for calculating the d-orbital energy levels of transition-metal ions in coordination polyhedra with both orthogonal and non-orthogonal distortions, using equations based on those derived by Ballhausen (1954). The input data are atomic coordinates, a standard value of the crystal field splitting parameter Δ at known metal-ligand distance, and the ratio of radial integrals B2/B4, which is approximately constant for a given ion. The method can be applied to polyhedra containing different ligands.

Application of the equations to the Mn3+ (M3) site in piemontite and the Fe2+ (M2) site in orthopyroxene gives calculated transition energies in good agreement with the observed band energies.

The calculations permit definite assignment of the great majority of d-d absorption bands even in multi-site phases, and enable discrimination of crystal-field and charge-transfer bands in mineral spectra. They also throw light on the fine structures of both oxygen → metal and metal → metal charge-transfer bands, and allow the calculation of crystal-field stabilization enthalpy and electronic entropy. The latter is a previously neglected energy term that contributes significantly to the energetics of reactions within and between phases containing transition-metal ions.

The solidus temperatures (IPTS-68) and melilite compositions (mole %) determined for some four-phase assemblages in the system CaO-MgO-Al2O3-SiO2 are: anorthite, diopside, spinel melilite (Åk81Geh19), 1236·5 °C; diopside, spinel, forsterite, melilite (Åk83Geh17), 1238 °C; foresterite, spinel, monticellite, melilite (Åk82Geh18), 1351 °C; monticellite, merwinite, spinel, melilite (Åk52Geh48), 1378 °C; dicalcium-silicate, Ca5MgSi3O12, spinel, melilite (Åk5Geh95), ca. 1412 °C; dicalcium-silicate, Ca6MgAl8SiO21, spinel, melilite (Åk4Geh96), ca. 1347 °C.

Without direct evidence that cations favour particular sites in the octahedral layers of phlogopite-biotite micas, it is usually assumed that the cations are distributed randomly. Such a distribution, however, implies appreciable populations of cation combinations that seem electrostatically improbable. A computer program was written that rearranges a random distribution so that the improbable combinations of cations are eliminated by predetermined restrictions. Its use shows that conditions deduced from Pauling's electrostatic valence rule lead to grouping of trivalent cations around vacancies; for some chemical compositions, chains of alternate trivalent cations and vacancies extend through the structure.

A number of minerals and residual glasses from absarokites, shoshonites, and latites have been analysed by electron probe.

Clinopyroxenes show very little iron-enrichment and these rocks are thus distinguished from tholeiites and alkali basalts.

Glasses from this group are also distinct from tholeiites and alkali basalts and occupy a separate field on a CaO-Na2O-K2O diagram.

Electron-probe data are presented for coexisting magnetite and ilmenite from seven gabbro cumulates and a gabbro pegmatite, and bulk FeO-Fe2O3-TiO2 analyses for ten magnetite-ilmenite assemblages. The oxides equilibrated at 580 to 720 °C and oxygen fugacities of 10−15·0 to 10−20·5 bar. Late-stage alteration, associated with growth of hydrothermal silicates, resulted in the breakdown of ilmenite to rutile and the dissolution of magnetite. Higher levels in the intrusion equilibrated at lower temperatures than deeper levels. All features described are consistent with the retention of the initial water content of the magma within the walls of the intrusion.

Two different spinels, analyses of which are given, occur in the layered ultramafic rocks at Dawros. Chrome spinel occurs both as gravity-stratified cumulates and as complex orbs, while an Al-rich spinel is both in rocks of the main Dawros magmatic sequence and in an association with an aluminous bronzite, which may originate by recrystallization. It is concluded that while the chrome spinel is certainly of magmatic origin, the aluminous spinel is probably partly of magmatic and partly of recrystallization origin.

Aguilarite, Ag4SeS, occurs in a hydrothermal vein deposit associated with sphalerite, chalcopyrite, galena, and native silver. Physical and chemical data agree with descriptions from Guanajuato (type locality). Differential thermal analysis of synthetic material indicates an inversion temperature of 122±1 °C. The mineral crystallized late in the paragenetic sequence, probably slightly above 200 °C.

Biphosphammite, NH4H2PO4, recorded once as secondary powder in 1870, occurs with bat guano in Murra-el-elevyn cave, 31° 20′ S., 126° 0′ E., Western Australia.

The mineral occurs as tapering tetragonal prisms with pyramidal terminations, which are colourless to light buff, very soft, water soluble, contain fine syngenite inclusions, and have D 2·04, ω 1·525, ε 1·480 Space group. , a 7·4935 Å, c 7·340 Å, six strongest powder X-ray lines 3·75 Å (10) 200; 5·24 Å (9) 101; 3·02 Å (9) 112; 1·993 Å (8) 312,213; 2·65 Å (7) 220; 2·368 Å (7) 310,301. Partial analysis of purest available material gave: P2O5 51·1, K2O 14·2, (NH4)2O 12·3, SO2 5·59, Na2O 0·16, water-insolubles 0·81 per cent, remainder mainly CaO and H2O. Calculated mineral content is 88 % biphosphammite (62 % NH4H2PO4, 38% isomorphous KH2PO4), 11·5% syngenite, insolubles 0·81 % calc. total 100·3 per cent.

Material proposed to be neotype is preserved at the Government Chemical Laboratories, Perth, Western Australia.

Green calcium sulphosilicate layers were formed in lime-larnite-calcite wall coating in a lime kiln at Rivervale, Western Australia. The compound formed in the kiln flame area by the combination of siliceous lime sand feed with sulphur trioxide from the sulphurous oil fuel.

The calcium sulphosilicate is orthorhombic with a 10·183, b 15·408, c 6·825 Å, space group Pcmn. Crystals are [100] tablets or prisms elongated along c, D 2·95, hardness 5, streak pale green, decomposed by organic acids. Optical properties α 1·632 = [001] blue, β 1·638 = [100] yellow-green γ 1·640 yellow-green, 2Vα = 60°, dispersion r > v, X-ray powder lines: 2·855 (10) 032,202; 2·838 (7) 330,321; 3·35 (6) 012; 2·622 (6) 331; 2·571 (6) 060; 3·20 (5) 231; 1·962 (5); 1·899 (5); 1·896 (5); 1·372 (5).

Chemical analysis by P. Hewson gave: SiO2 21·50, Al2O3 1·83, Fe2O2 0·50, CO2 0·49, P2O5 0·23, CaO 57·19, MgO 0·35, Na2O 0·22, K2O 0·22, SrO 0·15, Li2O 0·06, SO3 16·71, H2O+ 0·28, H2O− 0·10, others 0·04, total 99·87. On a water-free basis the unit cell contains Ca19.66 Mg0.17 Na0.14 K0.08 Sr0.03 Li0.08 approximately 4[Ca5(SiO4)2SO4] and isostructural with silicocarnotite, 4[Ca5(PO4)2SiO4]. Type material is preserved at the Government Chemical Laboratories, Perth, Western Australia.