Several discordant, garnet-bearing bodies are described from the St. Just part of the Land's End granite aureole, Cornwall. It is suggested that these formed by a combination of metasomatic replacement and dilation with concomitant precipitation. Other Ca-Fe aluminosilicates (containing large amounts of Zn, Sn, B, and Be) are also present in the bodies. The chemical, petrographic, and field evidence suggests that the introduced material was transported by hydrothermal fluids. These fluids could well be related to the intrusion of the granite and the earliest phases of ore mineralization. Chemical analyses of garnets, calcic amphiboles and one apatite, epidote, diopside, and axinite are given.

Phosphorites from the continental shelf off Morocco have been analysed for major elements and Fe, Mn, V, Cu, Ni, Zn, As, Na, Sr, S, and for carbonate. In pyritic phosphorites Cu, Ni, Zn, and As are present mainly in minor pyrite and organic carbon. In ferruginous phosphorites As, Mn, and V are associated with goethite. In the ferruginous phosphorites Cu, Ni, and Zn may have been introduced in association with organic matter and pyrite during phosphorite formation and been retained during subsequent destruction of these phases by weathering. In all phosphorites Na and Sr are present mainly in carbonate-fluorapatite. Sulphur in the ferru-ginous phosphorites occurs only in carbonate-fluorapatite. In the pyritic samples it is partitioned between pyrite and francolite (carbonate-fluorapatite).

Tučekite, Ni9Sb2S8, was found as microscopic grains in a mineralized Archaean chlorite schist at Kanowna (35° 35′ S., 121° 36′ E.), Western Australia, and in the gold-bearing conglomerates of the Witwatersrand System (26° S., 27° E.), South Africa.

The nickel mineralization at Kanowna is located in metamorphosed basic and ultrabasic rocks of the Morelands Formation, which is part of the Kalgoorlie-Yilgarn succession of the West Australian Archaean shield. The tučekite-bearing mineralization occurs as an approximately 2 cm thick zone of disseminated sulphides in a chlorite schist near its contact with a serpentinized ultramafic intrusive rock. Tučekite is here associated with millerite, pyrite, chalcopyrite, gersdorffite, pentlandite, magnetite, and supergene polydymite. Tučekite occurs as rims and irregular grains partly replacing millerite, and was apparently formed during the later stages of the ore-forming process by reaction of Sb-bearing solutions with millerite.

In the Witwatersrand the mineral was found in a heavy mineral concentrate prepared from ore from the Vaal Reef, Vaal Reefs mine, Klerksdorp (Far West Witwatersrand), and in a mixed concentrate from the Carbon Leader Reef and the Ventersdorp Contact Reef, Western Deep Levels Ltd., Carltonville (West Wits Line). Although rare free grains of tuSekite are found, the mineral is more commonly intergrown with gold, and in the Vaal Reef the mineral is also found intergrown with gersdorffite.

Empirical formula of the Kanowna mineral is (Ni, Fe, Co)9·05(Sb, Bi, Te)1·00(Sb, As)1·04S8; that of the Witwatersrand mineral is (Ni, Fe)9·00(Sb, Bi)1·00(Sb, AS)1·06S8. The structural formula is assumed to be ; Z = 1. The mineral is opaque, has a metallic lustre, and is pale yellow. Under the microscope in reflected light it is pale brownish-yellow; bireflectance not discernible; anisotropy very strong with deep brown and greyish-blue polarization colours; reflectivity high. Indentation hardness 718 kg/mm2 (20 g load); 417 kg/mm2 (10 g load).

Strongest Debye-Scherrer powder-pattern lines of the Witwatersrand mineral are 2·76 (10) 211; 2·38 (8) 112; 2·28 (8b) 221, 310; 1·850 (8) 222; 4·33 (7) 101; 1·793 (7) 400, 3o2. By analogy with hauchecornite, the pattern can be indexed on a tetragonal unit cell with a = 7·174 Å and c = 5·402 Å; ρ (calc.) = 6·15 g/cm3. Type material is preserved in the British Museum, London, and the National Museum, Prague (Czechoslovakia).

Psilomelane has been shown to be orthorhombic with a 8·254, b 13·40, c 2·864 Å. by the application of Lipson's method. The indexing of powder photographs of psilomelane , where R″ includes the bivalent metals Mn, Ba, Ca, Mg, Co) indicates the space-group P21212 (D22) with one molecule per unit cell. Indexing of powder photographs of psilomelane is not satisfactory with Vaux's axes. Fermor's ‘psilomelane’ is cryptomelane, which is tetragonal with a 9·822, c 2·858 Å. Cryptomelane (KR8O16, where R stands for Mn in different valency states, partly replaced by other cations) is body-centred tetragonal with one molecule per unit cell. Fermor's stalactitic ‘psilomelane’ has an inner dull core of cryptomelane and an outer fine-grained crust of pyrolusite in each needle-shaped body.

Cuspidine was first described by Scacchi (1876) in the ejected blocks of metamorphosed limestone at Vesuvius, but a detailed and systematic morphological description of well-terminated crystals was given first by vom Rath (1883) from material at Cozzolino in Resina, Vesuvius. The monoclinic character of the spear-shaped crystals was then established with a:b:c = 0·7243:1:1·9342, β = 89° 22′, and twins on (100) giving = 1° 16′. Scacchi (in Arzruni, 1877) had earlier indicated the possibility that cuspidine he had described as orthorhombic was monoclinic and twinned when he recognized a re-entrant angle of 178° 42′ on the cleavage truncating the acute ends of the crystals.

Eggletonite is a new mineral, the Na analogue of ganophyllite. Type material has composition

(Na0.82K0.40Ca0.39□0.39)Σ2.00 (Mn6.61Zn0.08Mg0.16Fe0.61Al0.56)Σ8.02 (Si10.33Al1.67)Σ12.00[(O28.92(OH)3.08]Σ32.00 (OH)4.00·10.66H2O.

It occurs as prismatic crystals elongated along [100] in miarolitic cavities in nepheline syenite at the Big Rock Quarry, Little Rock, Arkansas. Single-crystal X-ray diffraction data are consistent with space group I2/a or Ia; a = 5.554, b = 13.72, c = 25.00Å, β = 93.95° Z = 2; this is equivalent to the substructure of ganophyllite. Physical properties include cleavage: {001} perfect; colour: dark brown; translucent; streak: light brown; hardness (Mohs): 3–4; brittle; observed density 2.76, calculated density 2.76 g/cm3. Optically, eggletonite is biaxial negative, with optical parameters 2Vα = 9(3)° r < ν, weak; indices of refraction α = 1.566(2), β = 1.606(2), γ = 1.606(2); pleochroism is very weak, γ ≃ β > α; α = pale brown to colourless, β ≃ γ = pale yellow brown. Principal lines in the X-ray powder diffraction pattern are (d, I/Io): 12.4, 100; 3.45, 15; 3.13, 30; 2.854, 15; 2.691, 25; 2.600, 20; 2.462, 20; 2.387, 15. The name is in honour of Dr Richard A. Eggleton, Australian National University.

The Fe 2p X-ray absorption spectra of single crystal gillespite, BaFeSi4O10, show a strong linear dichroism, i.e. a large difference in the absorption when measured with the polarization of the X-rays either parallel or perpendicular to the plane of the FeO4 group. The isotropic spectrum, obtained from measurement at the ‘magic angle’, and the polarization dependent spectra have been compared to atomic multiplet calculations and show an excellent agreement with theory. Analysis of the branching ratio, the linear dichroism, and the detailed peak structure confirms that the 5A1 level is the ground state at room temperature and pressure. The 5B2 level is sufficiently low in energy that a distortion of the electronic charge density, induced by increased pressure, may result in a 5B2 ground state.

Pilawite-(Y), ideally Ca2(Y,Yb)2Al4(SiO4)4O2(OH)2, was discovered in a pegmatite near Piława Górna, Lower Silesia, Poland. The mineral occurs as white, translucent, brittle crystals up to 1.5 mm in size. It has a white streak, vitreous lustre and a hardness of 5 on Mohs scale. The calculated density is 4.007 g/cm3. Pilawite-(Y) is non-pleochroic, biaxial (+), with refractive indices α = 1.743(5), β = 1.754(5) and γ = 1.779(5), birefringence Δ = 0.03–0.04, 2Vmeas. = 65(2)° and 2Vcalc. = 68°. Pilawite-(Y) is monoclinic P21/c, with unit-cell parameters a = 8.558(3) Å, b = 7.260(3) Å, c = 11.182(6) Å, β = 90.61(4)o, V = 694.7(4) Å3. The crystal structure was refined to an R1 index of 2.76% and consists of chains of edge- and corner-sharing octahedra decorated by tetrahedra and having the stoichiometry [Al2(SiO4)4O(OH)] that link by sharing corners to form an octahedron–tetrahedron framework with large interstices that contain Ca2+ and (Y,Ln)3+. It is a graphical isomer of the Al–P framework in palermoite, Sr2Li4[Al2(PO4)2(OH)2]2. The pilawite-(Y)-bearing assemblage began crystallization at high Y + Ln activities and was modified progressively by a Ca-enriched fluid, resulting in the sequence: keiviite-(Y) → gadolinite-(Y) to hingganite-(Y) + hellandite-(Y) → pilawite-(Y) → allanite-(Y) → epidote/zoisite.

In the aureole of the late Caledonian Omey granite corundum develops in the Dalradian country rocks in a zone up to 250 m from the granite contact. The distribution of andalusite and K-feldspar in pelites and calcite+wollastonite+grossularite in marbles is consistent with inner-aureole metamorphic conditions of 615±25°C at 2.5±0.25 kbar, and ⋍ 0.85. Corundum develops from the reaction muscovite → corundum + K-feldspar+H2O and first appears over 100 m further from the granite than the assemblage wollastonite + grossularite + anorthite. Experimentally determined equilibria can be satisfied only if for the corundum-producing reaction was less than 0.6 and perhaps as low as 0.4. Corundum always grows within large muscovite crystals;fH2O within the crystal lattice is unrelated to that in the grain-boundary fluid of the surrounding rock.

Although whole-rock oxidation ratios are irregularly distributed within the aureole they are uniformly low in corundum-bearing rocks. Reducing conditions probably resulted from localized flow of H2O-rich fluid away from the granite in a diffuse channelway that contains most of the corundum localities and also a distinctive skarn. Although corundum growth within muscovite is sealed off from the external water vapour conditions, it is suggested that movement of H2O down a thermal gradient (and hence down an fH2O gradient at constant pressure) promotes the escape of (OH)− from the muscovite lattice and so allows the corundum reaction to proceed.

Very little reformation can now be gathered about a remarkable shower of meteoric stones that fell many years ago in a remote district in south-west Queensland. Only a few scraps of information have appeared in print, and these are largely contradictory. However, some very tangible evidence arrived unexpectedly at the British Museum in 1935 in the form of a remarkable collection of 102 complete meteoric stones with a total weight of 107¾lb. This material had been in the possession of Mr. Benjamin Dunstan, formerly Government Geologist of Queensland, who had been collecting information of the fall with a view to writing up an account for publication. This unfortunately he never did, and much of the information is now lost. The specimens were offered to the British Museum by his widow, but they came along quite casually as an appendix to a collection of fossils.

Carlfriesite is a new species found in relative abundance at the Bambollita (now La Oriental) mine in the Sierra La Huerta near Moctezuma, Sonora. Colour primrose yellow (R.H.S. 4B) with pale yellow streak. H = 3½, Dmeas = 6·3, Dcalc = 5·93. Fair cleavage on {010}. Monoclinic with a 12·585 Å, b 5·658, c 9·985, β 115° 35′. Space group Cc or C2/c. Strongest lines are 3·167 (10), 3·082 (9B), 5·063 (6), 2.832 (6), 3·369 (4), 4·825 (3), 2·698 (3), and 4·o89 (2). Feeble pleochlroism in pale yellow with γ > α = β α = 1·982, β = 2·095, γ 2·19 2Vα, = 79° calc. Occurs with cerussite and chlorargyrite in an oxidized assemblage derived from hessite, galena, and bornite.

Leószilárdite (IMA2015-128), Na6Mg(UO2)2(CO3)6·6H2O, was found in the Markey Mine, Red Canyon, White Canyon District, San Juan County, Utah, USA, in areas with abundant andersonite, natrozippeite, gypsum, anhydrite, and probable hydromagnesite along with other secondary uranium minerals bayleyite, čejkaite and johannite. The new mineral occurs as aggregates of pale yellow bladed crystals flattened on ﹛001﹜ and elongated along [010], individually reaching up to 0.2 mmlong. More commonly it occurs as pale yellow pearlescent masses to 2 mm consisting of very small plates. Leószilárdite fluoresces green under both longwave and shortwave ultraviolet light, and is translucent with a white streak, hardness of 2 (Mohs), and brittle tenacity with uneven fracture. The new mineral is readily soluble in room temperature H2O. Crystals have perfect cleavage along ﹛001﹜, and exhibit the forms ﹛110﹜,﹛001﹜,﹛100﹜,﹛101﹜ and ﹛101﹜. Optically, leószilárdite is biaxial (-), α= 1.504(1), β= 1.597(1), γ= 1.628(1) (white light); 2V (meas.) = 57(1)°, 2V (calc.) = 57.1°; dispersion r > v, slight. Pleochroism: X= colourless, Y and Z= light yellow; X<Y ≈ Z The average of six wavelength dispersive spectroscopic analyses provided Na2O 14.54, MgO 3.05, UO3 47.95, CO2 22.13, H2O 9.51, total 97.18 wt.%. The empirical formula is Na5.60Mg0.90U2O28C6H12.60, based on 28 O apfu. Leószilárdite is monoclinic, C2/m, a = 11.6093(21), b = 6.7843(13), c = 15.1058(28) Å, β = 91.378(3)°, V= 1189.4(4) Å3 and Z = 2. The crystal structure (R1 = 0.0387 for 1394 reflections with Iobs > 4σI), consists of uranyl tricarbonate anion clusters [(UO2)(CO3)3]4- held together in part by irregular chains of NaO5(H2O) polyhedra sub parallel to [010]. Individual uranyl tricarbonate clusters are also linked together by three-octahedron units consisting of two Na-centred octahedra that share the opposite faces of a Mg-centred octahedron at the centre (Na–Mg–Na), and have the composition Na2MgO12(H2O)4. The name of the new mineral honours the Hungarian-American physicist, inventor and biologist Dr. Leó Szilárd (1898–1964).

The Raman spectrum of holmquistite, a Li-containing orthorhombic amphibole from Bessemer City, USA has been measured. The OH-stretching region is characterized by bands at 3661, 3646, 3634 and 3614 cm−1 assigned to 3 Mg–OH, 2 Mg + Fe2+–OH, Mg + 2Fe2+–OH and 3 Fe2+–OH, respectively. These Mg and Fe2+ cations are located at the M1 and M3 sites and have a Fe2+/(Fe2+ + Mg) ratio of 0.35. The 960–1110 cm−1 region represents the antisymmetric Si–O–Si and O–Si–O stretching vibrations. For holmquistite, strong bands are observed around 1022 and 1085 cm−1 with a shoulder at 1127 cm−1 and minor bands at 1045 and 1102 cm−1. In the region 650–800 cm−1 bands are observed at 679, 753 and 791 cm−1 with a minor band around 694 cm−1 attributed to the symmetrical Si–O–Si and Si–O vibrations. The region below 625 cm−1 is characterized by 14 vibrations related to the deformation modes of the silicate double chain and vibrations involving Mg, Fe, Al and Li in the various M sites. The 502 cm−1 band is a Li–O deformation mode while the 456, 551 and 565 cm−1 bands are Al–O deformation modes.

This paper reports an investigation of the crystallization products of K-rich silicate and carbonate melts trapped as melt inclusions in clinopyroxene phenocrysts from the Dunkeldyk alkaline igneous complex in the Tajik Republic. Heating experiments on the melt inclusions suggest that the carbonate melt was formed by liquid immiscibility at 1180°C and ∼0.5 GPa. The carbonate-rich inclusions are dominated by Sr-bearing calcite, and rich in incompatible elements. Most of the silicate minerals are SiO2-poor and rich in K, Ba and Ti. Leucite, kalsilite and aegirine are the earliest magmatic minerals. High Ba and Ti contents in the melt resulted in the crystallization of Ba-rich K-feldspar, titanite, perovskite and Ti-bearing garnet, and the rare Ba-Ti silicates fresnoite and delindeite. The last minerals to crystallize from volatile-rich melts and fluids were aegirine, götzenite, K-Ba- and Ca-Sr-bearing zeolites, fluorite and strontium-rich baryte. Interaction of the early minerals with residual melts and fluids produced Ba-rich phlogopite and Sr-rich apatite.

Hydration processes of primary anhydrous minerals as well as dehydration of the hydrated phases are relevant not only for answering geochemical and petrological questions, but are also interesting in the context of the theory of the ‘Evolution of minerals’. Our study of the evolution of anhydrous exhalative sulfates in hydration and dehydration processes has demonstrated the complexity of the processes for a number of minerals from the active high-temperature fumaroles of Tolbachik volcano (chalcocyanite Cu(SO4), dolerophanite Cu2O(SO4), alumoklyuchevskite K3Cu3AlO2(SO4)4 and itelmenite Na2CuMg2(SO4)4). Hydration and dehydration experiments were carried out for all four minerals using powder X-ray diffraction. A typical structural characteristic of several anhydrous copper sulfate minerals of fumarolic origin is the presence of oxygen-centred OCu4 tetrahedra. These are absent in the structures of all known hydrated minerals or synthetic compounds of the class under consideration. Hydration of minerals initially containing O2– anions as part of oxocomplexes, proceeds with sequential formation of a large series of hydroxysalts. On the contrary, hydration of itelmenite with its relatively complex ‘initial’ structure, but without additional oxygen atoms that are strong Lewis bases, results in formation of simpler hydrates. The lower the temperature and the larger the excess of water, the stronger the tendency of the cations to adopt higher hydration numbers thus outcompeting the sulfate anions as ligands. Ultimately, the water molecules completely expel the bridging sulfate anions from the metal coordination sphere yielding relatively simple fully hydrated structures.

It is common practice to estimate a mean diameter for spherical or sub-spherical particles or vesicles in a rock by multiplying the average diameter of the approximately circular cross-sections visible in thin section by a factor of 1.273. This number-weighted average may be dominatedby the hard-to-measure fine tail of the size distribution, and is unlikely to be representative of the average particle diameter of greatest interest for a wide range of geological problems or processes. Average particle size can be quantified in a variety of ways, based on the mass or surfacearea of the particles, and here we provide exact relations of these different average measures to straightforward measurements possible in thin section, including an analysis of how many particles to measure to achieve a desired level of uncertainty. The use of average particle diameter isillustrated firstly with a consideration of the accumulation of olivine phenocrysts on the floor of the 135 m thick picrodolerite/crinanite unit of the Shiant Isles Main Sill. We show that the 45 m thick crystal pile on the sill floor could have formed by crystal settling within about a year.The second geological example is provided by an analysis of the sizes of exsolved Fe-rich droplets during unmixing of a basaltic melt in a suite of experimental charges. We show that the size distribution cannot be explained by sudden nucleation, followed by either Ostwald ripening or Browniancoalescence. We deduce that a continuous process of droplet nucleation during cooling is likely to have occurred.

In order to define the cathodoluminescence (CL) properties of magmatic topaz and its relation with trace-element composition, we studied topaz phenocrysts from the Ary-Bulak ongonite massif, Russia using a wide array of analytical techniques. Scanning electron microscopy CL panchromatic images reveal strong variations, which define micrometre-scale euhedral growth textures. Several truncations of these growth textures occur in single grains implying multiple growth and resorption events. The CL-spectra of both CLbright and -dark domains have a major peak in the near-ultraviolet centred at 393 nm. Cathodoluminescence images taken after several minutes of electron bombardment show decreasing emission intensity. Electron microprobe analyses indicate high F concentrations (average OH/(OH + F) = 0.04 calculated by difference, 100 wt.% – total from electron probe microanalyses), consistent with what has been found previously in topaz-bearing granites, and the OH stretching vibration (∼3653 cm–1) was detected in Raman spectra. Laser ablation inductively-coupled plasma mass spectrometry traverses performed across the CL textures detected trace elements at ppm to thousands of ppm levels, including: Fe, Mn, Li, Be, B, P, Nb, Ta, W, Ti, Ga, light rare-earth elements, Th and U. Lithium, W, Nb and Ta appear to be correlated with CL intensity, suggesting a role for some of these elements in the activation of CL in topaz. In contrast, no clear correlation was found between CL intensity and F contents, despite the fact that the replacement of OH for F is known to affect the cell parameters of topaz.

Major, trace element composition and Sr isotopic data were collected for gabbroic rocks, plagiogranites and albitites in the ophiolite assemblage from Swat Valley (NW Frontier Province, Pakistan). Petrographic study revealed that these rocks were subjected to important structural and mineralogical modifications due to greenschist-epidote-amphibolite facies sub-sea-floor metamorphism and to brecciation. On the other hand, the examination of whole rock chemical composition and of chemical trends showed that these rocks were affected by some chemical modifications, concerning especially Na2O, K2O and Rb. The very low contents of HFS (high field strength) and RE elements found in gabbroic rocks and plagiogranites were considered to be a primary magmatic feature pointing in part to their cumulitic nature and in part to an origin from a refractory parental magma. The Sr isotopic data indicate that gabbroic rocks and plagiogranites were subjected to exchange with sea water. The particular chemical features shared by gabbroic rocks and plagiogranites suggested that fractional crystallization was a possible evolution process. In contrast, albitites are characterized by anomalously high contents in HFSE and LREE and by values of the 87Sr/86Sr ratio very close to sea water. These features suggest a more complex origin with respect to gabbroic rocks and plagiogranites.

Several cordierites from pegmatites were found by emission spectroscopy to contain as much as 0·7 wt. % of BeO. Structural crystallographic considerations suggest that the beryl molecule, Be3Al2Si6O18, may have appreciable solubility in the structure of cordierite. Some hydrothermal experiments carried out on this assumption indicated about the same amount of BeO substitution in the magmatic temperature range as is shown by the pegmatite cordierites. The natural BeO-bearing cordierites have distinctive infra-red absorption properties, which are reproduced in the synthetic solid solutions.

The nucleation and growth behaviour of the (Mn,Ca)CO3 solid solution from aqueous solutions in silica hydrogel were studied at 25ºC. In order to obtain different levels of supersaturation at nucleation, experiments were carried out in diffusion columns of different lengths. Zoning phenomena, compositional heterogeneity and morphological modifications of the crystals obtained were examined by electron microprobe and scanning electron microscopy and microanalyses. The large difference between the solubility of calcite (CaCO3) and rhodochrosite (MnCO3) implies a significant preferential partitioning of Mn towards the solid. The distribution of Mn2+ and Ca2+ ions between the aqueous and solid phase demonstrates that at elevated supersaturation, this preferential partitioning is softened. The morphologies of experimentally grown individuals show a clear dependence on the composition of the parent solution. Crystals obtained from aqueous solutions with large Mn contents exhibit a relatively sharp concentric zoning along the equatorial sections. On these bases, the roles of multiple kinetic and thermodynamic factors during nucleation and growth are also discussed. Finally, an X-ray diffraction analysis of the precipitates provided no evidence of the formation of the dolomite-type ordered kutnahorite [CaMn(CO3)2] in any of the experimentalsets.