Almost 400 specimens of natural and synthetic quartz were γ-irradiated and then heated. Polarized absorption spectroscopy, EPR, and spectrochemical analysis were used to investigate the various colors produced.

A blue color originated from absorption by the A1 and A2 bands at 1·85 and 2·55 eV. The substitutional A1 EPR hole-type center usually considered to be the cause of the color in smoky quartz does not correlate with A1 and A2, but with A3, a previously unreported absorption band at 2·90 eV. The A1 and A2 absorptions bleach at temperatures as low as 280 °C and as high as 360 °C the range for A3 being 140 to 380 °C. The B band at 3·95 eV was previously reported only in irradiated fused silica.

Greenish-yellow colors (appearing yellow when of low intensity) were observed after irradiation (followed by heating in some instances) in many specimens of natural and synthetic quartz; the color originates from the tail of a strong absorption band in the ultraviolet. The bleaching temperature range is the same as that for A2.

The wide variation in color of natural and irradiated smoky quartz can be explained by combinations of the smoky (A3), blue (A1 and A2), and greenish yellow absorption features.

Investigation of serpentine minerals from metaserpentinized ultramafic rocks in two Archaean green-stone belts, east of Kalgoorlie, has indicated that antigorite, exhibiting a very wide range of textures in thin section, is the dominant serpentine species; however, it is locally accompanied by relict lizardite. Chrysotile occurs both in late tectonic veins and as a present-day weathering product of relict olivine. Analytical data and structural formulae on seven serpentines, characterized independently by X-ray diffraction analysis, support the chemical differences between antigorite and chrysotile postulated by earlier workers.

The changes in olivine morphology and grain size upwards through comb-layered olivine eucrite and peridotite varieties of harrisite in the Rhum layered pluton are systematic, from abundant small granular crystals, to fewer and larger hopper crystals, to highly elongate branching crystals, which are preferentially elongate along the a axis and perpendicular to the plane of the layering. These changes have been reproduced in the laboratory by cooling water-bearing melts (P = 5 kb) of harrisite at 14 and 30 °/hr. These cooling rates represent maximum values for natural crystallization of comb-layered harrisite. Other experiments suggest that the oriented branching olivines in the rock crystallized at 30–50 °C supercooling. The results indicate that continuous, rather than abrupt, changes in the degree of supercooling and supersaturation of the magma can cause formation of comb layers. They also indicate that while field relations point to growth of most comb layers along a thermal gradient in the magma, this is not an essential condition for comb layer formation. Growth could be along a compositional gradient instead. During crystallization of a comb layer, both nucleation rate and the number of crystals suspended in magma close to the layer are essentially zero. Conditions initiating and terminating comb layer formation and the origin of the rapid vectorial crystallization are discussed. It is suggested that some comb layers could form without change in degree of supercooling, due to rapid removal of crystals suspended in the magma causing the enhanced growth rate and branching style of growth of the remaining crystals. Multiple origins of comb-layered rocks may therefore be possible.

Zincian högbomite has formed by hydrous alteration of spinel and biotite in a lens of highly aluminomagnesian sapphirine-bearing granulite-facies rocks. The högbomite forms chestnut-brown {0001} flakes 1 mm across. ε = 1·827, ω = 1·852 (− 0·002). Analysis: BeO 0·10, SiO20·65, Al2O3 59·69, TiO2 5·37, Ga2O3 0·23, Nb2O5 0·01, Fe2O3 5·24, SnO2 0·06, NiO 0·04, ZrO2 0·03, MgO 7•69, Sc2O3 0·01, CoO 0·11, ZnO 3·08, FeO 17·52, In2O3 0·05, MnO 0·12. The pattern of d-spacings is anomalous. Other högbomites from the region have exsolved from cordierite or titaniferous opaque oxides.

Analyses are presented for an iron-rich pentlandite associated with native copper and troilite from New Zealand and three cobalt-bearing pentlandites from Australia. Examination of 141 published analyses indicates that pentlandites, regardless of their Co content, can be classified on the basis of cell size, Fe content, Fe:Ni ratio, and the sulphide assemblage in which they occur. The cobaltian varieties show two separate trends.

Electron-microprobe analyses of chromites from the Helgeland area, Norway, show that they are all low in zinc. Many chromites show physical properties identical with donathite (anisotropism; polar magnetism) but have cubic lattices. One exception, from Rødøya, shows an unusual deviation from cubic symmetry and that there may exist complex intergrowths of two different tetragonal lattices and a cubic lattice. The similarity between the chromites studied and donathite suggests that the chemistry and crystallography of that mineral may be more complex than is currently accepted.

Chloroxiphite, Pb3CuO2(OH)2Cl2, is monoclinic, space group P21/m, with a = 10·458, b = 5·750, c = 6·693 Å, β = 97·79°, Z = 2. The structure has been refined by the method of least squares from three-dimensional Mo-Kα intensity data to a conventional R value of 0·115. The structure consists of sheets of composition [Pb3 CuO2(OH)2]2−, in themselves made up of the layer sequence Pb-(O, OH, Cu)-Pb, lying parallel to (01). The structure contains eight-fold PbO4Cl4 and seven-fold PbO5Cl2 polyhedra common in other oxychlorides, Pb6 clusters and copper atoms in square planar, Cu(OH)4, coordination.

The crystal structure of killalaite has been approximately determined, using a crystal from the original locality. The ionic constitution is Ca3+x (H1–2xSi2O7) (OH), with x ≈ 0·2 for the crystal studied. Crystal data are: monoclinic pseudo cell with a 6·807, b 15·459, c 6·811 Å, β 97·76°, space group P21/m, Z = 4, Dx-ray = 2·94 gcm-3. Additional, very weak reflections indicate a B-centred monoclinic true cell with doubled a and c. The structure was determined using only the pseudo cell reflections, and includes one fractionally occupied Ca site; the larger true cell possibly arises from ordering of Ca atoms in these sites, together with associated small shifts of other atoms. There are weak indications that the degree of occupancy of this site may be variable. The X-ray powder pattern has been indexed and a calculated pattern is also given. A synthetic compound called ‘Phase F’ by Aitken and Taylor (1960) appears identical with or closely similar to killalaite.

Bandy (1938) described as metavoltine? a mineral coming from Chuquicamata (Chile) with chemical composition K2Na6Fe3+(SO4)12(OH)2·20H2O. Owing to some differences between this mineral and that first described by Blaas (1883), doubts persist on the identity of these two compounds. X-ray analyses were performed to clarify the relation between them. An artificial product, closely related to metavoltine as regards lattice and chemical composition, was also studied, and affords a better understanding of the Na and K diadochy already observed in metavoltine.

Ferrinatrite crystallizes in space group P, with a = 15·566(5), c = 8·69(1) Å, and Z = 6. The crystal structure was solved by three-dimensional Patterson and Fourier syntheses, and refined by least squares employing 2378 independent reflexions to a final R value of 0·068. The iron ions occupy special positions and are surrounded octahedrally by oxygen atoms. Fe3+O6 octahedra and SO4, tetrahedra are linked together to form infinite chains of Fe-O-S linkages in the [0001] direction. These chains are linked to each other by [NaO5(H2O)2] polyhedra and probably by hydrogen bonds. The topology of the arrangement is the same as that of the hypothetical P312 structure proposed by Moore and Araki (1974).

Smolyaninovite, (Co, Ni, Ca, Mg)3 (Fe, Al)2 (AsO4)4. 11H2O, has recently been recognized in the mineralized region around Mount Cobalt, Queensland. It is a soft polycrystalline earthy yellow-brown material, is probably the weathering product of cobaltian arsenopyrite or alloclase, and shows para-magnetic properties.

Motukoreaite occurs as relatively abundant, white, clay-like cement in both beach-rock and basaltic volcanic tuffs on the flanks of a small, extinct, late Pleistocene, basaltic cone at Brown's Island (Motukorea), within Waitemata Harbour, Auckland, New Zealand (36° 50′ S., 174° 35′ E.). The occurrence was originally recorded by Bartrum (1941) as ‘beach limestone’ found at two places of the island's shore. The beach-rock consists of a grain-supported fabric of poorly sorted, well-rounded, alkali-olivine basalt pebbles and granules, subangular to sub-rounded fresh olivine sand and abraded sand- and gravel-sized bioclasts in a colourless to pale yellow-green aphanocrystalline matrix of motukoreaite. Additional detritals include quartz, feldspar, and sedimentary rock fragments. Stereoscan examination of the surface of pieces of the cement prised from the beach-rock showed a box-work of plate-like crystals with a hexagonal form in which individuals measured about 3×3×0·02 microns (fig. 1).

Wet-chemical analysis of a separate of the cement containing some 5 % quartz and traces of calcite and goethite gives SiO2 5·55, Al2O3 17·87, Fe2O3 0·73, CaO 0·92, MgO 22·98, MnO 0·70, ZnO 0·56, Na2O 0·71, K2O 0·10, CO2 9·32, SO3 10·00, H2O+ 19·62, H2O- 10·35, sum 99·41 %. The unit-cell formula using obtained unit-cell constants and measured specific gravity 1·43) is (Na0·73K0·07)∑0·80(Mg18·13Mn0·32Zn0·21)∑18·66Al11·15(CO3)6·22(SO4)3·97 (OH)51·1927·20H2O. Of several idealized formulae that may be proposed NaMg19Al12(CO3)6.5 (SO4)4(OH)54·28H2O is preferred.