A nephelinite from the extinct volcano Mt. Shaberu, North Kivu, Belgian Congo, contains two new minerals: Götzenite is triclinic with a 10·93, b 7·32, c 5·74 Å, α 90°, β 100°, γ 120°; the unit-cell contents approximate to (Ca,Na,Al)7 (Si,Ti)5O15F3·5, and the optical constants are α 1·660, β 1·662, γ 1·670, 2Vγ 52°; sp.gr. 3·138. Götzenite is related to the rinkite series, and, less closely, to wollastonite and pectolite. Combeite is rhombohedral, space-group R3m, R32, or R¯3m, a 10·43, c 13·14 Å., the unit cell containing approximately 3[Na4(Ca,Al,Fe)3Si6O15(O,OH,F)2]; optically uniaxial positive, ε = ω = 1·598±0·002; sp.gr. 2·844.

Coexisting calcium-rich and calcium-poor pyroxenes have been separated from the gabbros and ferrogabbros of the Skaergaard layered basic intrusion and chemically analysed. Nine new analyses of augites, three of inverted pigeonites, and one of orthopyroxene are presented, together with optical properties. The trend of crystallization of the augites is different from that drawn by previous investigators. The stages at which the orthopyroxene and pigeonite begin and cease to erystallize are defined, and the sub-solidus exsolution and inversion textures of the pigeonites are examined in detail. The characters of the exsolution textures and the degree of pigeonite inversion (monoclinic to orthorhombic pyroxene) are shown to change gradually with height in the intrusion, and are related to a gradual change in the interval between the temperatures of crystallization and inversion.

Morphological characters of zircons in concentrates have been studied by measurement of length along the c-axis and breadth along the a1- or a2-axis of 200 doubly terminated crystals for each sample. The sample is represented graphically by a line fitted mathematically to a scatter plot of the measurements. This line, the reduced major axis, is visualized as a growth trend, and samples are described and compared statistically.

From a careful study of zircons in a tonalite it is concluded that zircon crystallized over a short range before crystallization of the main constituent minerals.

The distribution of zircon in a batholith of magmatic origin has also been studied. The batholith grades from a core of granodiorite to a mantle of tonalite, but the zircons are uniform throughout. Small bodies of granodiorite and quartz monzonite have sharp contacts against the main batholithic rocks, and zircon samples from these intrusives differ from one another and from those of the batholith. It is concluded that the batholith represents a single intrusion which differentiated after emplacement, and that the later intrusives each crystallized under different conditions.

The presence of garnet in acid rocks of the charnockite series south of Madras is reported. Petrographic deseriptions of garnetiferous enderbites and related pyroxene-granulites, khondalites, and leptynites are accompanied by new chemical analyses of 6 rocks, 8 garnets, and 5 orthopyroxenes from the type area near Madras, and from Ceylon, Varberg, and Uganda. The garnets show a considerably higher FeO/MgO ratio than the coexisting ortbopyroxenes and the host rocks. The presence or absence of garnet appears to be related to the bulk chemistry of the rocks. Basic garnetiferous granulites associated with these rocks are considered to represent an unstable mineral assemblage and may be genetically unrelated to the acid types. Attention is drawn to the prevalence of enderbitic rocks in the type area.

Isokite (CaMgPO4F), a new mineral homologous with sphene, was described late in 1955 from a Rhodesian carbonatite plug. A fine-grained variety is now reported from Bohemia, where it occurs as a replacement of (probably a hydrothermal alteration product of) coarse medium brown ‘later’ triplites. It is intimately associated with fine-grained apatite that along with quartz formed post-isokite.