The temperature at which dehydroxylation occurs in amphiboles is thought to be largely dependent on the type of cation that occupies the M3 and M1 sites. Four amphibole types have been studied in which these sites are occupied, in various proportions, by Mg2+ or Fe2+. The temperature of dehydroxylation, in an inert atmosphere, is shown to rise with increasing Mg2+ content in these sites.

Numerous authors have attempted to use chemical composition as a means of distinguishing amphibolites derived by isochemical metamorphism of basic igneous intrusives or flows from those of sedimentary parentage. In recent years contributions have come from Engel and Engel (1951, 1953, 1962), Lapadu-Hargues (1953, 1958), Poldervaart (1953), Eckelmann and Poldervaart (1957), Wilcox and Poldervaart (1958), Evans and Leake (1960), and Walker, Joplin, Lovering, and Green (1960).

Image analysis techniques are used to quantify finite strain in microconglomerates from the ‘Zone Houillère’ (Briançonnais Zone, French Alps) using the normalized Fry method. Two different techniques have been developed to extract the necessary parameters from quartz grains: the first uses an interactive videographic image analyser linked to a digitizer, and the second uses a semi-automatic image analyser algorithm working on numeric images. Comparison between these two techniques allows the data provided by the latter to be validated. Semi-automated image analysis is then employed to compute the characteristics of the finite strain ellipse as defined by the normalized Fry method. This has been tested on natural and simulated fabrics and gives accurate results. Finally, these techniques have been applied to samples from the French Alps, in an attempt to correlate the regional pattern of finite strain with deep seismic reflectors. This paper presents the preliminary results using finite strain data determined by image analysis processing.

The western Rhodope massif contains a significant number of ‘battery grade’ Mn-oxide deposits which are best developed in the area near Kato Nevrokopi, Drama district, N. Greece. Economic Mn-oxide ore concentrations are confined to fault zones and related karsts in marbles. The mineralisation has formed by weathering of hydrothermal veins that were genetically related to Oligocene magmatism.

At Kato Nevrokopi, progressive and continuous weathering of primary, hydrothermal veins of rhodochrosite, mixed sulphide, quartz and ‘black calcite’ (calcite and todorokite) has resulted in the formation of the assemblage MnO-gel-(amorphous Mn-oxide)-todorokite-azurite-goethite-cerussite in the veins and the assemblage MnO-gel-nsutite-chalcophanite-birnessite-cryptomelane-pyrolusite and malachite and amorphous Fe-oxides in karstic cavities.

The fs2 and fO2 of the hydrothermal fluids increased with time. The breakdown of the hypogene Mn-carbonate was aided by the production of an acidic fluid due to the oxidation of sulphides. Precipitation of the supergene ores was caused by neutralisation of the fluids due to reaction with the host marble and to mixing of relatively reduced fluids with oxygenated surface water in a fluctuation water table regime. Zinc was also mobile during weathering and became concentrated in the intermediate Mn-oxides, effectively stabilising their structures. The mineral paragenesis records the progressive oxidation of the ore and the appearance of less hydrated Mn-oxides, low in alkalis and alkaline earths.

The studied gabbroic nodules occurring in the Petrazza pyroclastic rocks consist mainly of plagioclase (An95–87), olivine (Fo83-73) and clinopyroxene (Mg# 90–77), with subordinate opaques (Ti-magnetite) and amphibole (Mg-hastingsite), which constitute the cumulate minerals. Interstitial material has a relatively high, but variable, degree of vesicularity and consists of variable amounts of glass and quenched crystals of plagioclase (An71–55), amphibole, clinopyroxene and rare biotite, olivine and opaques. Silicate melt inclusions are abundant in the cumulate minerals, but complete homogenization to melt has been observed only in the inclusions occurring in clinopyroxene, where the temperatures of homogenization vary from 1134 to 1190°C. Microthermometric investigations of fluid inclusions and of the shrinkage bubble of the melt inclusions suggest that the magma contained CO2. The apparent scarcity of H2O indicates that this component was strongly partitioned into the magma at the time of crystallization of the investigated minerals; this is further supported by the occurrence of (1) daughter biotite- and amphibole-bearing inclusions which show that the H2O activity in the magma was sufficiently high to allow their crystallization, and (2) calcic plagioclase (An95–87) which can be crystallized from a high-alumina basaltic magma at pressure ≤2 kbar, temperatures in the range 1050–1100°C and in the presence of 3–4 wt.% of water (MELTS software simulations).

The composition of the melt inclusions suggests that the hosting plagioclase, olivine and clinopyroxene crystallized from slightly different batches of magma. The S content in the melt inclusions of clinopyroxene and olivine is high (up to 0.41 wt.%). The presence of Fe-Cu(-Ni)-rich blebs of sulphide in plagioclase, olivine, amphibole, and locally in the melt inclusions too, further supports the important role of sulphur in the primitive magmas of the investigated gabbros. Small differences in redox conditions or in the Fe content of the melts favoured S mobilization as sulphide.

Amphiboles in dykes from the dominantly silica-undersaturated Monteregian series range from pargasitic megacrysts and xenocrysts to kaersutitic, pargasitic and hastingsitic phenocrysts, groundmass prisms and reaction rims. Amphiboles in dykes and plutons from the silica-oversaturated White Mountain Magma Series range from kaersutite, through hornblende, hastingsite and edenite, to sodic-calcic and sodic varieties. This contrast between the amphiboles from the two series is probably a reflection of differing melt silica activity and is a useful petrologic discriminant. In most cases, pargasitic amphibole megacrysts from Monteregian monchiquites reflect the Mg numbers of their host rocks and are considered cognate. The megacrysts are lower in Ti and higher in Mg and Al than their phenocryst mantles and rims. This is probably a result of higher pressures of formation.

Ab initio total energy calculations based on the local density approximation (LDA) and using a conjugate-gradient solver for the Kohn-Sham equations have been performed for cordierite, brucite, (Mg(OH)2) and diaspore (AlOOH). The calculated fractional coordinates of all structures are in good agreement with experimental diffraction data. The angle of the non-linear hydrogen bond in diaspore is reproduced well. The Raman active OH stretching frequency in brucite has been calculated using the frozen phonon approach and the calculated stretching frequency is in very good agreement with the observed value. The energetically most favourable calculated orientation of the proton-proton vector of an H2O molecule incorporated in the structural channels of cordierite agrees with findings deduced from spectroscopic data, and the calculated energy of hydration is in reasonable agreement with calorimetric data. It is therefore concluded that ab initio total energy calculations can confidently be used to predict properties of hydrogen bonded structures, which is difficult with conventional parameterized static lattice energy minimization calculations. An extension to the model is necessary to improve the agreement of the predicted to the observed lattice parameters for small structures.

The prismatic variety of fluoro-edenite, a new amphibole found in lavas from Mt Etna in Biancavilla (Catania Province, Sicily, Italy), has been characterized by μ-Raman and μ-FTIR spectroscopy. The wavenumbers at which the bands are detected in the μ-Raman and μ-FTIR spectra are compared with tremolite, asbestos the chemical and crystallographic characteristics of which are very similar to those of fluoro-edenite.

Two Ca-Zr-Ti oxides, zirconolite CaZrTi2O7 and calzirtite Ca2Zr5Ti2O16, occur as minute interstitial crystals in skarn (forsterite-spinel-calcite, with rhythmic banding) ejecta from the 1631 eruption of Vesuvius. The substitutions in zirconolite observed here mainly include Nb-for-Ti (typical for zirconolites in alkaline magmatic surroundings) and (Th,U)-for-Ca, and produce a crystal-chemical formula Ca0.9–1Th0.04–0.12U0.04–0.10ZrTi1.36–1.61Nb0.09–0.22(Fe,Mg,Al)0.29–0.47O7. The skarn, which occurs in contact with a pyroxenite of magmatic origin, displays a mineralogical zoning with Zr-, Ti-, Nb- and (U,Th)-rich oxides (e.g. Nb-perovskite and zirconolite) close to the pyroxenite (<2 mm), whereas those oxides observed further from the pyroxenite (>1 cm) are richer still in Zr but (Ti, Nb, U, Th)-poor or free (e.g. calzirtite and baddeleyite ZrO2). Textural relationships between minerals provide evidence for a metasomatic development of the skarn at the expense of the pyroxenite, through drastic leaching of Na, K, Si, Fe. The same process is responsible for the zoning in the skarn (leaching of Fe, Si, Ti, Nb, U and Th), in which Zr was less mobilized than other HFSE. This process, related to the circulation of fluids equilibrated with carbonates, is responsible for those forsterite-spinel (± calcite) skarns which can be observed as remnants in a large part of the 1631 ejecta. Such endoskarns probably formed repeatedly during at least the last millennia of Vesuvius’ history, and existed prior to the emplacement at shallow depth of the 1631 magma whose chamber walls were different from the limestone/dolostone classically assumed to host the Vesuvius magmas (Fulignati et al., 2005).

The superstructure of ganophyllite has been analysed using subcell single crystal X-ray data and electron-optical observations. The full cell (supercell), space group A2/a, a = 16.6, b = 26.6, c = 50 Å, β = 94° has the approximate formula (K,Na,Ca)6+7.5(Mg,Fe,Mn)24[Si32.5Al7.5]O96(OH)1621H2O, Z = 8. A structure is proposed in which triple chains of silica tetrahedra parallel to X form narrow 2 : 1 layers with sinusoidal Mn-octahedral sheets. The triple chains are connected laterally, and across the interlayer, by pairs of inverted tetrahedra, linking to each other into four-member rings parallel to (010). Polytypes are generated by various displacements of the inverted tetrahedra.

The crystal structure of epistilbite ((Ca2·59Na1·06K0·10) (Al6·29Si17·71O48).15·74H2O; C2/m; a = 9·08, b = 17·74, c = 10·25±0·01 Å; β = 124·54±0·05°) was determined by 3-D least-squares methods. The alumino-silicate framework is composed of 4-, 5-, and 8-membered rings of tetrahedra. There are two sets of intersecting channels each defined by 8-membered rings. The (Ca, Na) atoms in the channels are in contact with seven water molecules and two oxygen atoms giving a coordination of nine at a cut-off distance of 2·77 Å. The average tetrahedral distance is lower than for anhydrous framework alumino-silicates but consistent with some other zeolite structures. Partial Al-Si ordering exists with one tetrahedron occupied preferentially by aluminum. This tetrahedron contains the two oxygen atoms that are coordinated with the (Ca, Na) atom.

The X-ray work described below has been done on crystals of bredigite obtained from two different sources, the natural mineral from Scawt Hill, County Antrim, and the synthetic mineral from spiegeleisen slags. Both types of material have been fully deseribed by Tilley and Vincent (1948). Their analysis shows that the slag mineral is a calcium orthosilicate in which Ca is partly replaced by Mg, Mn, and Ba, the extent of the replacement being represented by the formula (Cal.59Ba0.08Mg0.31Mn0.09)SiO4. Tilley and Vincent conclude that this orthorhombic (pseudo-hexagonal) phase is identical with the high-temperature form α' of pure Ca2SiO4, the existence of which was suggested by Bredig (1943a), and confirmed by TrSmel (1949) using a high-temperature powder camera. Bredig (1943a) also suggests, on the basis of a comparison of X-ray powder patterns, that the crystal structure of α'-Ca2SiO4 is similar to that of β-K2SO4. The present single-crystal work was originally undertaken in order to investigate the structure of α'-Ca2SiO4 more fully.

In May, 1936, a quantity of pale yellow, rounded fragments, averaging 7 mm. across, was submitted to us by Mr. Arthur Russell for examination, with the information that the material came from the Castle-an-Dinas wolfram mine, and contained bismuth and tungsten. Chemical and spectroscopic examination showed that, besides bismuth and tungsten, the mineral contained only traces of silicon, arsenic, and iron. A sample of the same material had also been given to the British Museum by Mr. E. H. Davison in 1934 and registered provisionally as bismuth tungstate. This, however, would not have provided sufficient of the yellow mineral for chemical analysis. We are also indebted to Mr. Davison for a further generous supply of yellow pellets picked from the wolfram concentrates received since tile present work was begun. The mineral has all the attributes of an alteration product probably of native bismuth. It is fine-grained and compact, with hardness 3½, and on fracture it gives a clay-like odour. Some of the pellets show traces of a micaeeous mineral and quite frequently enclose native bismuth, wolframite, and bismuthinite. Mr. Russell has picked out from tihe material he had collected a few green pellets and some showing both the yellow and the green mineral. Spectrographs of the two are identical, but an X-ray powder photograph of the green mineral is quite distinct from that of tile yellow mineral.

The crystal structure of macphersonite (Pb4SO4(CO3)2(OH)2, Pcab, a = 9.242(2), b = 23.050(5), c = 10.383(2) Å) from Leadhills, Scotland has been determined to an R = 0.053. The structure has many features in common with its polymorph leadhillite including three distinct types of layers. Layer A includes sulphate tetrahedra, Layer B is composed of Pb and OH, while Layer C is composed of Pb and CO3 with topology identical to that in cerussite. In both macphersonite and leadhillite these layers are stacked along [010] as …BABCCBABCC… The double CC layer is almost identical in the two structures and forms a structural backbone and occurs in other structures including hydrocerussite and plumbonacrite. The sulphate layer shows the greatest difference between the two structures and can be described by a pattern of up or down pointing tetrahedra. For macphersonite the sequence along [001] is …UDUDUD… while in leadhillite the sequence along [010] is …UDDUUDDU… This latter sequence effectively doubles b relative to the equivalent direction in macphersonite. Susannite, a third polymorph, may have yet another sequence of sulphates to give trigonal symmetry; by heating leadhillite, displacive movements of sulphate groups may occur with a conversion to susannite.

Examination of published procedures for the decomposition and subsequent analysis of chromite and chrome ores shows some to be unnecessarily complicated and time consuming. Others fail to yield consistent and reproducible results. Decomposition is rapidly and effectively accomplished using the peroxide frit technique of Rafter. Chromium may then be removed and determined volumetrically allowing the rest of the analysis to proceed along conventional silicate lines. Fe2+ is determined by oxidimetry following digestion with a mixture of phosphoric and sulphuric acids in the presence of ceric sulphate.

Copper mineralization at Tomnadashan is associated with granitic lenses intruded into a small Caledonian diorite body. The mineralization occurs as disseminations and irregular veinlets and mainly comprises pyrite, chalcopyrite, tetrahedrite-tennantite, calcite, and quartz. There are small inclusions of bismuthinite, galena, aikinite [(Cu,Pb,Fe,Bi)S3], and a mineral with a chemistry similar to hodrushite (Cu8Bi12S22). The tetrahedrite contains up to 6.1 wt. % bismuth.

Four km to the south, at Corrie Buie, are quartz veins, hosted by meta-limestones, containing galena with minor amounts of chalcopyrite, pyrrhotite, sphalerite, electrum, schirmerite, and lillianite homologues.

The mineralogy of both deposits is consistent with that associated with acid magmatism. There are mineralogical similarities between the two deposits but the style of mineralization at Tomnadashan suggests a limited hydrothermal system and therefore the Corrie Buie veins may be related to felsic intrusives to the south.

We present an assessment of the thermo-elastic behaviour of rutile based on X-ray diffraction data and direct elastic measurements available in the literature. The data confirms that the quasi-harmonic approximation is not valid for rutile because rutile exhibits substantial anisotropic thermal pressure, meaning that the unit-cell parameters change significantly along isochors. Simultaneous fitting of both the diffraction and elasticity data yields parameters of KTR0= 205.14(15) GPa, KSR0= 207.30(14) GPa, $K_{TR0}^{\prime} $= 6.9(4) in a 3rd-order Birch-Murnaghan Equation of State for compression, αV0= 2.526(16) × 10–5 K–1, Einstein temperature θE = 328(12) K, Anderson-Grüneisen parameter δT = 7.6(6), with a fixed thermal Grüneisen parameter γ = 1.4 to describe the thermal expansion and variation of bulk modulus with temperature at room pressure. This Equation of State fits all of the available data up to 7.3 GPa at room temperature, and up to 1100 K at room pressure within its uncertainties. We also present a series of formulations and a simple protocol to obtain thermodynamically consistent Equations of State for the volume and the unit-cell parameters for stiff materials, such as rutile. In combination with published data for garnets, the Equation of State for rutile indicates that rutile inclusions trapped inside garnets in metamorphic rocks should exhibit negative residual pressures when measured at room conditions.

Parasibirskite, with the ideal formula Ca2B2O5·H2O, is a new mineral species found at Fuka, Okayama Prefecture, Japan. It is a polymorph of sibirskite, CaHBO3, and occurs as subparallel aggregates of tabular crystals up to 40 × 20 × 3 µm in size. Associated minerals are takedaite, olshanskyite, sibirskite, frolovite and calcite. The mineral is white, and has a weak pearly luster. Optically, the mineral is biaxial positive, α 1.556(2), β 1.593(2), γ 1.663(2) (λ 589 nm). The Vickers microhardness of aggregates is 121 kg mm−2. The mineral is monoclinic with space group of P21/m, a 6.722(4), b 5.437(2), c 3.555(2) Å, β 93.00(5)°, V 129.8(2), Å3. The strongest lines in the X-ray powder pattern [d in Å (I)(hkl)] are 2.237(100)(300), 6.73(70)(100), 2.975(60)(011), 3.354(30)(200), 2.855(20)(210) and 1.776(20) (002). Wet chemical analysis, electron-microprobe analysis and ICP emission spectrometry give the values CaO 56.06 %, B2O3 34.10 %, H2O 9.97 % and total 100.13%. The empirical formula calculated on the basis of O = 6 is Ca1.985B1.945O4.901·1.099H2O, for Z = 1, Dcalc 2.54 and Dmeas 2.50(1) g cm−3. Parasibirskite is formed by hydrothermal alteration of takedaite.

The various (P, T) stability fields of iron-free zoisite have been deduced for systems containing excess silica and water with Ca : Al ratios ranging from 1 : 2 (anorthite) to 3:2 (grossular). Zoisite is a possible phase in all systems with Ca:Al lower than 3:2, attaining its maximum stability at the zoisite (Ca:Al = 2:3) and prehnite (Ca:Al = 2:2) compositions.

The consequences of varying the Al : Fe ratio are next examined. Zoisite with 4 % pistacite is stable to 525° at 2 kilobars, compared with ∼585° for clinozoisite and 620 to 630° for epidote (Ps35) at the same pressure. Increasing iron content also stabilizes epidote minerals relative to their low-temperature and high-pressure decomposition products.

Examples of natural zoisite-clinozoisite, zoisite-epidote, and clinozoisite-epidote assemblages are described. It is concluded that zoisite-epidote mixtures result from the disproportionation of clinozoisite outside its own stability field, but within those of zoisite and epidote. The assemblage zoisite-clinozoisite is probably not stable, but further evidence is needed on this point. The assemblage clinozoisite-epidote is stable below 550° C, at which temperature the solvus in the Al-Fe series closes.

The low-temperature structural behaviour of natural cancrinite with a formula Na6.59Ca0.93[Si6.12Al5.88O24](CO3)1.04F0.41·2H2O has been investigated by means of in situ single-crystal X-ray diffraction and Raman spectroscopy. High quality structure refinements were obtained at 293, 250, 220, 180, 140, 100 and at 293 K again (at the end of the low-T experiments). The variation in the unit-cell volume as a function of temperature (T) exhibits a continuous trend, without any evident thermoelastic anomaly. The thermal expansion coefficient αV = (1/V)∂V/∂T is 3.8(7) × 10–5 K–1 (between 100 and 293 K). The structure refinement based on intensity data collected at ambient conditions after the low-T experiment confirmed that the low-T induced deformation processes are completely reversible. The extraframework population does not show significant variations down to 100 K. The strong positional disorder of the carbonate groups along the c axis persists within the T range investigated. The structural behaviour of cancrinite at low-T is mainly governed by the continuous framework rearrangement through the ditrigonalization of the six-membered rings which lie in a plane perpendicular to [0001], the contraction of the four-membered ring joint units, the decrease of the ring corrugation in the (0001) plane, and the flattening of the cancrinite cages. A list of the principal Raman active modes in ambient conditions is provided and discussed.