The alkaline volcanic rocks of Tenerife comprise a compositionally continuous series of ankaramites, alkali basalts, trachybasalts, trachyandesites, trachytes, phonolites, and peralkaline phonolites. Ca-rich pyroxenes occur as phenocrysts throughout the series. They show a limited range of composition from diopside and Ti-rich samite in the basic and intermediate rocks, to sodic sahlite in some phonolites. Features of both the sahlite-aegirine and sahlite-hedenbergite trends are present. Sodic ferrosahlites occur as xenocrystal 'green cores' in phenocrysts from some basic and intermediate rocks. The latter are associated with kaersutite xenocrysts and are similar to pyroxenes in some plutonic xenoliths from Tenerife. During the formation of the 'green cores' conditions were more reducing allowing pyroxene compositions to extend through the range sahlite-hedenbergite.

Aegirine-angite and Ti-rich aegirine are present in the groundmass of some phonolites and in pyroclastic boulders of nepheline syenite. The aegirines are associated with magnesioarfvedsonite and aenigmatite, and it is considered that they crystallized under conditions of low oxygen fugacity.

The composition of the various phases present in the rh6nite-bearing leucite basanites of the southern part of the Sillon Houiller district have been determined with the electron microprobe. Clinopyroxenes show strong progressive enrichment in Al2O3 and TiO2, maximum values being 13 % and 6 % respectively. These extreme compositions are comparable to others found in feldspathoidal lavas from other provinces, and can be explained by the low silica content of the liquids they crystallized from, and high cooling-rates. Rhönite composition is similar to those previously determined in various terrestrial occurrences. The chemical compositions of the lavas differ from those of basanites, and are intermediate as far as Ca, Al, and Si contents between basanites and melilite-bearing basic lavas. The presence of rhönite can be explained by bulk composition, but is not a consequence of a particularly high Fe and/or Ti content. Xenoliths are absent from these lavas, so that there is no petrographic indication of possible contamination. It is tentatively concluded that the high K/Na ratio is primary.

A metallographic investigation of macro- and micro-structures, supported by microprobe examination, has been made on similarly sized (< ca. 200 g) individual Cañon Diablo meteorites of rim or plains type. Plains type specimens show heat alteration zones of the ablation type. They are extensively cracked in a brittle manner and in some instances the cracks are penetrated by ablation melt product. In all cases the cracks are now penetrated by terrestrial corrosion. Cohenite and schreibersite are cracked in a brittle manner. By contrast the rim type specimens are remarkably free of internal cracking or corrosion penetration. Instead the cohenite, schreibersite, taenite, and kamacite are transected by slip faults or shear displacements along the line of which all phases appear to have slipped in a non-brittle manner. These specimens have all been subject to shock loading and particular attention is paid to the effects of shock on sphalerite, on cloudy taenite, and on martensitic plessite.

Plains specimens have broken from the original projectile in a brittle manner well above the earth's surface. Rim specimens have been scabbed from the rear of the projectile as it penetrated the earth's surface. Some of the rim specimens show signs of being heated by the blast of the crater-forming explosion.

The spectral reflectivities of homogeneous and exsolved titanomagnetites of the same chemical composition were measured in air and in oil. The reflectivities of the two kinds of titanomagnetite are closely similar in the blue part of the spectrum, but become increasingly different when proceeding towards the red end. The refractive indices (n) and the absorption coefficients (k) were calculated from the reflectivity values. The n-values of the two kinds of titanomagnetite show a pattern of separation similar to that of the reflectivity values. Regarding possible differences between the k-values no reliable conclusions could be drawn. Some possible explanations of the observed separations are discussed.

A phonolite dyke at Mount Goonneringerringgi, south-eastern Queensland, carries prominent pink specks of eudialyte, together with manganoan pectolite (ranging to calcian serandite), aegirine, albite, arfvedsonite, nepheline, natrolite, and analcime. This is the first confirmed occurrence of eudialyte in Australia

Microprobe analyses of eight ilmenites, a titaniferous magnetite, and a rutile are presented. They were synthesized at pressures from 5 to 26 kb and temperatures between 1075 and 1225°C in the anhydrous melting interval of a tholeiitic andesite from the Snake River Plain, Idaho, U.S.A. Both the Fe/Ti distribution between coexisting ilmenite and titanomagnetite at 11 kb/1075°C and the low calculated Fe3+ contents of the other ilmenites confirm previous suggestions that the fo2 in these experiments was buffered by graphite capsules to values near those generated by the wüstitemagnetite assemblage. Mn in the ilmenites (0·30-0·51% MnO) shows moderate negative correlations with both the pressures and temperatures of their formation, whilst Al (0·41-1·06 % Al2O3) shows poor positive correlations with these parameters. In contrast, the only significant trend shown by Mg in the ilmenites (2·09-5·26 % MgO) is with the position of each experimental run in the melting interval of the lava. Mg/(Mg + Fe2+) of the ilmenite decreases during equilibrium crystallization at a given pressure and appears to be controlled solely by Mg/Fe2+ distribution amongst the coexisting ferromagnesian minerals and interstitial liquid (glass).

It is proposed that mitridatite and englishite contain octahedral sheets of the alunite type and that their formulae are [Ca6(H2O)3(PO4)2][Fe3(OH)6(PO4)(PO3OH)]3 and [K2Na(H2O)4Ca4·5 (PO3OH)3][Al3(OH)6(PO4)(PO3OH)]3 respectively.

Hypogene alteration of ussingite from the southern part of the Ilimaussaq intrusion in South Greenland has resulted in the formation of three associations: gmelinite-apophyllite, gmeliniteherschelite- earthy-natrolite, and earthy natrolite alone. Ossingite reacted with late magmatic fluids, producing the secondary minerals either by in situ replacement of the ussingite or in cavities, which may be up to 3 cm across.

Compositions concerning sodic amphiboles (glaucophane) in the system Na2O-Al2O3-MgO-SiO2-H2O have been studied at PH2O ≤ 3 kb, 380 °C < T < 700 °C. The study attempts to establish the mineral parageneses under these physical conditions as they define the clay mineral (saponite-hectorite smectite) and greenschist (chlorite-albite) facies. The occurence of sodic amphiboles is defined by compositional parameters. Glaucophane does not appear in the present investigation.

The method of ‘reaction reversal’, i.e. using precrystallized mineral assemblages to form new ones, has been used to establish the three reactions: albite + chlorite → paragonite + saponite, paragonite + chlorite → saponite + cordierite, and saponite + paragonite → albite + cordierite. In general, the clay mineral → greenschist transformation is favoured by an increase in pressure in the system studied. The amphibole present is a sodic richterite with the type substitution

The mineral tacharanite has been recently re-examined by Cliff et al. (1975). They worked on material from the original locality, Portree, in Scotland (Sweet, I961) and from a few new European localities described between 1971 and 1974. None of the post-Sweet authors, however, refer to the second discovery of the mineral from Tasmania where it was identified by this writer in 1961 and recorded in a number of publications (Sutherland, 1965; Sutherland and Corbett, 1967; Sutherland and Hale 1970; Mines Department of Tasmania, 1970; Sutherland, 1973b). The first Tasmanian report was communicated to J. M. Sweet, who kindly arranged for the Department of Mineralogy, British Museum, to send the writer a small piece of the Portree material for study. As the Tasmanian find does not seem to be known in the later literature, some more detailed information on its occurrence is presented here for comparison with the European localities.