Major- and trace-element data are presented for basic dykes intruding the Eastern Red Hills district of the Tertiary igneous centre of Skye. In addition to a group of transitional basic intrusions, members of two other distinctive suites have been identified: (1) a series of basic alkaline intrusions (akin to the ‘Beinn Dearg Type’ of Harker, 1904), with characteristic high alkali contents, distinctive values of K2O/(K2O + Na2O) and rare-earth-element (REE) patterns similar to those of many of the Tertiary lavas of north Skye, and, (2) tholeiitic dykes, with low concentrations ofK2O, Ti/Zr values of c. 100, and flat REE patterns similar to those of the so-called Fairy Bridge magma type (Mattey et al., 1977). From these data and a consideration of the time relationships of the various components of the Skye Centre, agreement is found with Thompson et al.'s (1972, 1980) model of a mantle thermal anomaly which generates the magmatic sequence: transitional basic magmas, giving way to olivine-bearing tholeiitic magmas (at the culmination of the anomaly), and, finally, late-stage basic alkaline magmas at the end of the activity.

Fine radiating groups of columnar aragonite crystals occur in a basaltic pipe at Kulnura, New South Wales, associated with calcite in habits varying from simple rhombohedra to complex spherulitic groups. It is proposed that the presence of impurities, especially magnesium, induced the crystallization of aragonite and was also responsible for the variety of calcite crystal habits present. Two distinct growth environments are indicated: steam-explosion breccia pipes containing aragonite and calcite showing an advanced stage of spherulitic growth; and vesicles with calcite in varying stages of spherulitic growth. This paper presents a preliminary study based on available material and on observations made in situ while access to the locality was still possible.

The Zaisho meteorite, one of only four known pallasite falls, contains pyroxene, which is rare in pallasites, and it is only the fourth meteorite known to contain phosphoran olivine. Except for a recent report by Goodrich (1984) such olivine appears to be restricted to pallasites, and to those containing the rare Mg phosphate, farringtonite. It is unique among olivines in having P in tetrahedral sites and having vacancies, for charge balance, in octahedral sites. Zaisho also contains stanfieldite and a phosphate having a composition between that of stanfieldite and farringtonite. Its metallographic cooling rate is similar to that of many other pallasites, but its average olivine composition, Fa18.3, places it in a small group with more Fe-rich olivines than most pallasites.

Ca- and Na-rich pyroxene compositions of four agpaitic phonolites from the Cantal Volcano (France) have been studied. The pyroxenes from each sample show a range of compositions between X2+ pyroxencs (with X = Ca, Mg, Fe2+) and aegirine. The main substitution, X2+ by (Fe3+ + Na+), occurs when Na-Mg = 0.5, by which time Si is already equal to 2.0. The crystallization of Fe-Na-rich pyroxenes seems to be related to the increasing peralkalinity of the environment, in which the initially high temperature was suddenly reduced. Other factors, such as the structure of the liquid, are also considered.

Sub-greenschist facies metamorphism has produced unusual subcalcic, Fe-rich actinolitic amphiboles in meta-dolerites from the Glenrock Station area, NSW. They show edenite, riebeckite, ferri-tschermakite and Ti-tschermakite coupled substitutions. Their high Fe content is attributed to high aFe2+ and aFe3+ in the fluid phase produced during the breakdown of clinopyroxene, hornblende, magnetite, and ilmenite. The high aFe2+ led to Fe led to Fe2- occupying the B site, resulting in the formation of subcalcic amphiboles. Variation in aFe2+, aFe3+, aMg, aSi, aAl, and aCa, in different domains resulted in the crystallization of chemically inhomogeneous amphiboles.

The occurrence and genesis of Ca(OH)2 and Mg(OH)2 deposits associated with hyperalkaline groundwater from partly serpentinized ultramafic rocks in Northern Oman is reported. Two types of Ca(OH)2 deposit are differentiated; crystalline portlandite formed by the evaporation of Ca2+-2OH− spring waters, and a form of amorphous gel, not previously known in nature. The latter is a product of present-day low-temperature serpentinization. Mg(OH)2 (brucite) in both holocrystalline and gel forms is produced by mixing of Mg2+−2H surface waters with a Ca2+-2OH− groundwater in both surface and groundwater environments. These results indicate that significant differences exist between the processes of medium- and low-temperature brucite generation.

The powder diffractograms of twenty wet chemically analysed samples in the isomorphous triphylite-lithiophilite series and five synthesized members with Fe/(Fe + Mn) = 1, 0.75, 0.50, 0.25, and 0.0, were recorded. Their unit cell dimensions were accurately refined in order to find a reliable method for semi-quantitative determination of the divalent cation content of these minerals. A multivariate best fit analysis based on Kummell’s procedure shows the marked influence of Fe2+ and Mg2+ on the cell dimensions, as well as that of small amounts of Fe3+ substituting for Mn2+, following LiMn2+ → □ Fe3+. The best representation of the correlation between chemical composition and cell parameters is given by the equations:

a = 6.1041 − 0.0245 Fetot − 0.049 Mg2+

b = 10.4511 − Fetot − 0.082 Mg2+

c = 4.7400 − 0.0130(Fe2+ + Mg2+) − 0.025 Fe3+.

No evidence of non-linearity has been found for the variation of the three cell dimensions with the chemical composition. Assuming the absence of appreciable amounts of Mg2+, the following set of equations is proposed: Fetot = 41(6.104–a); Fetot = 35(10.451–b); Fetot = 77(4.740–c) in which the c dimension gives a relatively poor estimate.

Two sets of determinative graphs were constructed, one based on the cell parameter variation, and the other on the 311, 222, and 142 reflection angular positions, v. the total iron content of these minerals. These two methods, whose reliability is examined, can be used for determination of the divalent cation content, provided the samples contain less than about 0.5 wt.% Na2O, 0.5 wt.% CaO, and 3 wt. % Fe2O3, and are homogeneous.

A miscibility gap exists between titansahlite and late-stage titanian aegirine in a teschenitic sill, with coexisting kaersutite plotting between them. A second series of titansahlite-sodian-ferrosahlite-aegirine-augite is continuous.

Electron probe microanalyses carried out on thirty areas of lithiophorite (Al,Li)MnO2(OH)2 from five Australian localities indicate wide variations in its Ni, Co, Cu, and Zn content. The concentration of these elements varies inversely with the alumina content, though there is a marked change in their concentration at 18% alumina, suggesting the existence of two varieties of lithiophorite with differing concentration of transition elements. EPMA line scans also indicate definite changes in Co content in lithiophorite grains less than 0.2 mm in dimension. The variations in alumina and transition elements may be explained if lithiophorite is considered to be an irregular mixed-layer-lattice intergrowth of pure lithiophorite with members of the recently discovered asbolane-type minerals.

Most of 325 K-feldspars from the Hida metamorphic belt are characterized by diffuse 131 and 11 reflections. These K-feldspars are classified into eight obliquity types on the basis of the width of the 131 peak or the ratio of mean height of two outer peaks (131 and 11) to that of the middle composite peak. From the distribution of obliquity types and the microscopic characteristics of K-feldspars, this area is divisible into six zones.

The feature of each zone is shown by the frequency distribution of eight obliquity types in each zone, which reflects the strength of later retrogressive effects. The frequency distribution of Δ values in each of the types IV-VIII provides further information on later events.

The result of the K-feldspar study possibly indicates that the inversion of monoclinic to triclinic K-feldspar, characterized by the development of perthitic texture or crosshatched twinning, is sensitive to the degree of later retrogressive events. Some data on 2θ values of 04, 060 and 01 reflections in each types are presented.

Retzian-(La), ideally, Mn2La(AsO4)(OH)4, is a new rare-earth analogue of retzian and retzian-(Nd). It was found associated with willemite, calcite, and franklinite, in the Stealing Hill Mine, Ogdensburg, Sussex County, New Jersey, USA. Retzian-(La) is orthorhombic, space group Pban, with a = 5.670(7), b = 12.01(1), and c = 4.869(8) Å. The strongest lines in the X-ray powder diffraction pattern are (d,I/I0,hkl): 3.51 80 111, 2.715 100 131, 1.848 50 061, 1.456 40. Microprobe analysis yielded MnO 25.2, MgO 3.7, ZnO 1.2, As2O5 26.5, La2O3 10.6, Ce2O3 8.8, Nd2O3 8.2, Pr2O3 5.1, Sm2O3 2.2, Y2O3 2.5, H2O [7.7], sum = 101.7 wt. %, corresponding to an La-dominant member of the retzian series.

Retzian-(La) forms 0.5 mm euhedral crystals composed of the forms {001}, {010}, {110}, and {150}; the crystals have pseudohexagonal habit. It is reddish-brown, with vitreous luster, no cleavage, density > 4.2 g/cm3. Optically, it is biaxial, positive, 2V = 82° with α = 1.766, β = 1.773, and γ = 1.788. Dispersion is strong, r > v; pleochroism is very weak; orientation is X = c, Y= b, Z = a; absorption is Z > Y > X.

The chemistry of opaque spinel, delafossite (Cu2O·Fe2O3), cuprite (Cu2O), cassiterite, nickel-olivine (Ni2SiO4), and bunsenite (NiO) from some copper converter slags has been investigated by electron microprobe analysis. The spinel has a complex composition containing up to 33.89% NiO and 47.69% SnO2, ranging from essentially Ni2SnO4 to (Ni,Fe2+)O4. The associated delafossite contains up to 19.18% NiO and 38.15% SnO2. The chemical variation of the mineral phases is evaluated, and it appears that Ni2+ enters the spinel and delafossite to charge-balance the octahedrally coordinated Sn4+.

Tetrahedral framework compounds, as defined in this paper, generally exist as tilted and distorted versions of ideal fully expanded structures at room temperature and atmospheric pressure. How pressure, temperature, and composition (P, T, and X) affect the tilting and distortion is critically reviewed. It is shown that although the effects of P, T, and X on the cell parameters are broadly analogous, the underlying structural changes are generally different. An important, and frequently neglected thermal effect is the apparent shortening of the framework bonds by the anisotropic thermal motion of the framework oxygens. Tilting models of framework compounds are critically examined and their failure to match the observed structural behaviour is attributed to changes in tetrahedral distortion. For quartz it appears that during compression the change in tetrahedral distortion is virtually all angular (O-Si-O angles), whereas during thermal expansion the change in distortion is in the Si-O distances. Such behaviour may typify the behaviour of many other framework compounds but the structural data needed to establish this are lacking. The review is illustrated by reference to the quartz and cristobalite analogues; to the sodalite, leucite, nepheline, scapolite, and feldspar families; and to the nitrides and oxynitrides of silicon and germanium. It is concluded that our understanding of the structural behaviour of framework compounds is still superficial and that much theoretical and experimental work remains to be done.

The result of electron probe microanalyses, along with X-ray and optical data obtained for tin sulphides from two different localities in south-west England indicate that the mineral hitherto described from St Michael’s Mount as stannite is in fact kesterite, Cu2(Fe0.23Zn0.77)SnS4. The yellow ‘stannite’ reported from this locality proved to be stannoidite, Cu8(Fe2.39 Zn0.61)SnS2S12. Kesterite, Cu2(Fe0.09Zn0.90SnS4, and zincian stannite, Cu2(Fe0.63Zn0.38)SnS4, are also reported from Cligga Head. It is suggested that a more cautious approach should be taken in identifying these tin sulphides solely on their optical properties.

Clay minerals are the principal reactive, non-combustible, phases present in the pulverized coal burned in power station furnace units. Despite the short heating time involved, the clay mineral impurity is wholly transformed in the ignition.

Illitic clays are partially melted, fluxed by water and potash, to produce an alumino-silicate melt phase. The melt is frothed by the synchronous production of carbon dioxide in an iron oxide catalysed oxidation of associated carbonaceous matter. This produces the hollow, gasfilled, glass-walled spheres (cenospheres) characteristic of pulverized fuel ash (PFA). Partial, primary devitrification crystallization of mullite and quartz from the high-alumina glass is general and the extent of devitrification may influence the pozzolanic efficiency of the PFA cenospheres.

Without the advantage of potash fluxing, the kaolinite lattices are dehydrated and transformed, without melting, to amorphous aluminosilicate and crystalline mullite.

Oxidation of pyrite leads to coating of cenospheres by condensed magnetite and the emission of sulphur dioxide in the flue gases.

Caratiite is a sulphate-chloride of potassium and copper with ideal formula K4Cu4O2(SO4)4MeCl (where Me = Na and/or Cu); it formed as fine green acicular crystals in lava of the 1869 eruption of Mt. Vesuvius, Naples, Italy. Caratiite is tetragonal, space group I4; a 13.60(2), c 4.98(1) Å, Z = 2. The strongest lines of the powder pattern are [d Å, I, hkl]: 9.61 100 (110); 6.80 80 (200); 4.296 60 (310); 3.015 100b (420,321); 2.747 70 (411); 2.673 60 (510); 2.478 60 (002); 2.388 70 (431,501); 2.281 60 (600). The mineral is uniaxial positive, ω 1.598, ɛ 1.711; it does not fluoresce under either short- or long-wavelength ultra-violet light. The specific gravity is 3.0 (meas.) and 3.22 (calc.).

The crystal structure of caratiite, K4Cu4O2 (SO4)4MeCl (a 13.60(2), c 4.98(1) Å, Z = 2) was solved in space group I4 from single crystal data, and refined to R = 0.035 for 654Fo > 6σ(Fo). The atomic arrangement is characterized by Cu2O(SO4)2 chains parallel to [001], with Cu in (4 + 1) co-ordination and O surrounded tetrahedrally by four Cu atoms. These chains are interconnected by K atoms to a framework, the channels of which house the Me and Cl atoms. The nature of the Me atoms is not completely clear; most probably the position is half occupied by Cu, fully occupied by Na, or occupied by a mixture of the two.

The first occurrence of mpororoite and anthoinite outside the African Continent has been found in an altered skarn from the Kara mine, Tasmania, forming a white powdery mixture of the two minerals pseudomorphing scheelite. The wet chemical analysis of the mixture shows WO3, Al2O3, and H2O to be the essential constituents, proving the non-essential nature of Fe2O3 in mpororoite; the original mpororoite contained high Fe2O3 substituting for Al2O3. The thermal treatment of the mixture at 100°C for 6 hours in air brings about the conversion of mpororoite into anthoinite, which re-hydrates into mpororoite, although the associated anthoinite does not. The source of Al is ascribed to the decomposition of aluminian andradite in the skarn.

Phlogopite mica has crystallized from blast-furnace slags at atmospheric pressure. Its chemistry is characterized by an excess of Na and K over their normal stoichiometric content, which is attributed to a composite association between phlogopite and glass. The diffraction pattern indicates that the phlogopite has a preferred orientation around the a-axis. Scanning electron microscopy shows that this phlogopite consists of numerous small platelets, which probably have their a-axes aligned.

Baddeleyite was found during an electron microprobe study of kimberlite from the Benfontein Sills, which are famous for their igneous carbonate and cumulus features. Based on its close textural association with both groundmass and cumulus oxides (spinels, ilmenite, perovskite), the baddeleyite appears to be primary and crystallized directly from the kimberlite magma. The baddeleyite is remarkably pure, with average ZrO2 and HfO2 of 96.4±1.3 and 1.72±0.08 wt. % respectively. Minor element ranges found were: TiO2 0.32–0.80, CaO 0.31–0.80, FeO 0.43–1.31, MgO 0.06–0.24, SiO2 0.04–0.19, Cr2O3 0–0.07, and Al2O3 0–0.10 wt.%. Several additional trace elements were sought (Ce, Cs, Mn, Nb, Nd, Sr, Y, Yb, and U) but were not detected.