The Neoproterozoic Sevattur complex is composed essentially of calcite and dolomite carbonatites together with pyroxenites and diverse syenites. This work reports the compositions and paragenesis of different pyrochlore generations hosted by albitite veins in this complex. The pyrochlore are distinctive, being exceptionally rich in uranium (26 to 36 wt.% UO2). Five types of pyrochlore (Pcl-I to Pcl-V) are recognised on the basis of composition and texture. With the exception of Pcl-V, the majority of the pyrochlore (Pcl-II to Pcl-IV) are surrounded by a thick orbicular mantle of Ba-rich potassium feldspar. This mantle around Pcl-V is partially-broken. Pcl-I is restricted to the cores of crystals, and associated with Pcl-II and -III and is relatively rich in Nb (0.53–0.62 apfu) together with more A-site vacancies (0.37–0.71 apfu) compared to Pcl-II to Pcl-IV. Other pyrochlore (Pcl-II to Pcl-IV) are characterised by elevated Ca and Ti compared to Pcl-I, which are related to the (3Nb5+ + Na+ → 3Ti4+ + U4+) and (2Nb5+ → 2Ti4+ + Ca2+) substitutions, respectively. These substitutions represent replacement of Pcl-II to Pcl-IV. Alteration and Ba-enrichment in all the pyrochlore are marked by interaction with an externally-derived Ba-rich hydrothermal fluid following the (2Nb5+ → 2Ti4+ + Ba2+) substitution. This substitution, coupled with extensive metamictisation leads to the formation of Ba-rich (15.9–16.3 wt.% BaO) patchy-zoned Pcl-V. The orbicular mantles around Pcl-I to Pcl-IV have prevented extensive metamictisation and extensive secondary alteration compared to Pcl-V, where mantling is partially disrupted. The compositional and textural variation suggests that Pcl-II to Pcl-IV form by nucleation on Pcl-I, and are transported subsequently as antecrysts in the host albitite.

Wolfeite (Fe,Mn)2PO4(OH) and barbosalite FeIIFeIII2(PO4)2(OH)2 are the principal phases in phosphate pods from the core of a zoned altered granitic pegmatite at Thackaringa. Chemical analyses of the wolfeite show it to be Fe-rich and extends the triploiditewolfeite isomorphous series (Frondel, 1949) from ΣFe/Mn = 3·39 (this study) to greater than 100 (Clark and Couper, 1979).

The crystal structure of ceruleite, CuAl4[AsO4]2(OH)8(H2O)4, has been solved to an R1 of 0.0307, using the world's largest crystals from the Cap Garonne mine, France. Ceruleite crystallizes in space group P21/n, with the unit cell a = 7.2000(14), b = 11.345(2), c = 9.856(2) Å, β = 105.57(3)°, V = 775.6(3) Å3 and Z = 1. Ceruleite has a unique structure that consists of Al(O,OH)6 octahedra that are sharing edges to form rhombus-shaped tetramers. AsO4 tetrahedra share two corners with one such rhombus and the other two corners with each of two other rhombi, linking them into a very open mesoporous framework. Cu(OH)2(H2O)2 squares lie in the channels and link Al4 rhombi along || b. H2O molecules are also located in the channels.

Millsite, CuTeO3·2H2O, is a new mineral from Gråurdfjellet in Oppdal, Norway. It occurs as a minor secondary phase alongside teineite, other copper secondaries and relict primary tellurides in a boulder of quartz-rich granite, which is probably a glacial erratic. Millsite is bright cyan to royal blue in colour. The mineral is transparent to slightly translucent with a vitreous lustre and has a perfect (100) cleavage. It is brittle, has a conchoidal fracture and a pale green streak. Millsite is optically biaxial (+), α = 1.756(5), β = 1.794(5), γ = 1.925calc and 2Vmeas = 60(1)°. Millsite has monoclinic space group P21/c, with a = 7.4049(2) Å, b = 7.7873(2) Å, c = 8.5217(2) Å, β = 110.203(3)°, V = 461.17(2) Å3 and Z = 4. The empirical formula is Cu0.99(Te0.98Se0.02)O3(H2O)2. The five strongest reflections in the powder X-ray diffraction pattern are [dhkl in Å (hkl, Irel%)]: 6.954 (100, 100), 3.558 (012, 64), 2.838 (12$\bar 2$, 47), 2.675 (211, 43) and 3.175 (210, 39). The crystal structure has been determined to R1 = 0.016, wR2 = 0.036 and GooF = 1.049. The diagnostic structural unit of millsite consists of a Cu2O6(H2O)4 dimer that is decorated with four TeO3 groups connecting adjacent dimers and defining (100) heteropolyhedral sheets. These heteropolyhedral sheets are only connected by layers of structurally significant hydrogen bonds and correlate with the (100) cleavage. Millsite is a polymorph of teineite with a unique configuration of the M2O6(H2O)4 dimer that leads to a sheet topology. No isostructural selenium or tellurium analogue exists. The monoclinic polymorph (P21/c) of chalcomenite ‘monoclinic-CuSeO3·2H2O’ hereafter, ahlfeldite and MgSeO3·2H2O have M2O6(H2O)4 dimers, but their configuration differs significantly from that of millsite and leads to a framework topology rather than a sheet. Teineite does not have a dimeric structure and so is fundamentally different from millsite. The sheet topology of millsite appears to be unique among tellurites.

The transmission electron microscope is now used in a great variety of mineralogical and petrological contexts, The development of such applications over the past thirty years is illustrated by reference mainly to studies on serpentine and amphibole minerals.

Girdite, a mineral described byWilliams in 1979 from the Grand Central mine, Tombstone, Cochise County, Arizona, USA, has been re-examined by powder X-ray diffraction, single-crystal X-ray diffraction and electron microprobe. Type material from The Natural History Museum, London and the United States National Museum of Natural History (Smithsonian Institution) was examined. The original description of girdite is shown to have been based upon data obtained from at least two and possibly three different phases, one corresponding to ottoite and another probably corresponding to oboyerite, although the latter itself appears to be a mixture. The discreditation of girdite as a valid mineral species has been approved by the IMA-CNMNC, Proposal 16-G.

The infra-red spectrum and X-ray powder pattern of a chemically analysed specimen of leadhillite, a lead carbonate sulphate hydroxide mineral from Leadhills, Scotland, are shown to be different from those in the literature. The IR spectra of several specimens suggest that mutual replacement of SO4, CO3, and OH may occur in this mineral, and it is thought that this might be responsible for the observed variation in X-ray spacings.

The crystal structure of pyrostilpnite from the Plaka mine, Lavrion Mining District, Greece, was refined in the space group P21/c to a final R1 index of 0.0283 on the basis of 2047 reflections with Fo > 4σ(Fo) and 65 refined parameters. Unit-cell parameters of the crystal examined are a = 6.8629(6), b = 15.8800(14), c = 6.2711(5) Å, β = 117.087(2)°, V = 608.48(9) Å3 and Z = 4. Chemical data agree with the stoichiometric formula Ag3SbS3. The crystal structure reported previously was confirmed, although a higher precision of refinement was achieved. It can be described as formed by {010} slabs running along c and connected along a through relatively longer Ag–S bonds. The analysis of the atomic displacement parameters together with a refinement with higher order tensors in the expression of the structure factors revealed no hint for pyrostilpnite as an ionic conductor. A historical background of the ‘ruby silvers’ is also reported.

Rare earth elements (REEs, ‘lanthanides’) constitute a vital commodity for technological applications. Although these elements occur at trace levels in many minerals, they can comprise major constituents of low abundance phosphate, carbonate, silicate and oxide minerals, some of which form during granite weathering. REE-phosphate phases can be a source of phosphorus for essential biomolecules and certain REEs are required by some bacterial enzymes involved in the oxidation of methanol, an important compound in the global biogeochemical carbon cycle. The mechanisms that promote the dissolution of lanthanide phosphate minerals are largely unknown, but probably vary with the lanthanide phosphate mineralogy of weathered rock and soil. Here, we studied weathering of five I-type, three S-type and one A-type granite to determine the extent of weathering of primary REE- and/or P-bearing minerals apatite, allanite and monazite, and the formation of secondary REE/P-bearing minerals. We found evidence for greater mobilisation of REE and P in weathered I-type and A-type granites than in S-types, reflecting the higher solubility of apatite and allanite relative to monazite. Although monazite persisted in highly weathered S-type granites, some alteration was detected. Secondary REE/P-bearing minerals were not detected in two S-type profiles, while spherical secondary REE/P-bearing mineral aggregates were abundant throughout the third S-type profile. Secondary euhedral REE/P-bearing crystals were abundant even in the slightly weathered I-type and A-type granite material, yet they were not detected in the highly weathered material, indicating that these minerals had dissolved. Our findings indicate that mineralogy constrains substantially, but does not control completely, lanthanide availability as a function of degree of weathering. These results have implications for predicting REE and phosphate bioavailability in soils derived from granitic rock types and suggest that highly weathered I-type granites may provide inocula for bioleaching experiments.

Corundum with inclusions of enigmatic super-reduced minerals was found in mineral separates received as a result of alluvial sediment exploration near Mt Carmel, Israel by the Shefa Yamim Company. This corundum, registered as ‘Carmel sapphireTM’, has been an object of numerous publications by W. Griffin's scientific team, in which they propose a questionable hypothesis of sapphire formation at the crust–mantle boundary with the participation of CH4+H2 fluids. Typically the Carmel sapphire is in small fragments of breccia with white cement, which in the opinion of Griffin et al. is a carbonate-cemented volcanic ash. Our investigation of the ‘white breccia’ showed that it consists of unsorted angular fragments of Carmel sapphire from ~1 μm to 7 mm in size cemented by aluminium hydroxides (bauxite) and is a waste product of the fused alumina process, i.e. it has an anthropogenic origin. Phases typical for slags of fused alumina production and metallurgical slags were identified in the ‘white breccia’. Carmel sapphire has numerous microscopic spherical inclusions of Si–Fe alloy indicating that the removal of Si and Fe from the corundum melt occurred at a temperature >2000°С. Osbornite, TiN, from Carmel sapphire has a chemical zonation characteristic of osbornite from fused alumina with enrichment of central zones in carbon. Comparison of the growth heterogeneity of Carmel sapphire and ‘electrocorundum’ indicates that the crystallisation of the corundum melt proceeded in a similar way. Unfortunately, in the case of Carmel sapphire from the Carmel locality, the contamination of geological samples with anthropogenic material has led to popularisation of biased views.

The Duotoushan deposit is an important Fe–Cu deposit in the Aqishan–Yamansu metallogenic belt of eastern Tianshan, NW China. Magnetite occurs in two main habits which are common in many Fe–Cu deposits, i.e. platy (TD1 Mag) and granular magnetite (TD2 Mag) have been identified at Duotoushan. Platy magnetite shows two different zones (bright and dark) based on the observations by scanning electron microscopy. The bright part (TD1-L) is the main part of TD1 magnetite and lacks inclusions. The dark part (TD1-D) is very porous and has abundant tiny silicate inclusions. Granular magnetite is usually anhedral with obvious oscillatory zoning in back-scattered electron images. In general, the dark zones of magnetite are characterised by greater Si, Ca, Al and lesser Fe contents than the bright zones. In situ X-ray diffraction (XRD) analysis shows that the lattice parameter of TD1 magnetite is approximately equal to that of standard magnetite and slightly higher than that of TD2 magnetite, indicating that some cations with ionic radii smaller than those of Fe2+ or Fe3+ entered the magnetite lattice by simple or coupled substitution mechanisms in TD2 magnetite.

The results in the present study show that the effects of temperature and $f_{{\rm O}_ 2}$ on platy magnetite are very limited and the changing fluid composition might be the major controlling factor for the formation of Duotoushan platy magnetite. Although the possibility that mushketovite transformed from hematite cannot be excluded entirely, evidence from in situ XRD data, pore-volume ratio calculation and the growth habit of intergrown minerals indicates that platy magnetite (TD1) coexisting with amphibole was more likely to have been precipitated originally from hydrothermal fluid. This was then affected by changes in the fluid composition which consequently led to dissolution of primary magnetite (TD1-L) and re-precipitation of TD1-D magnetite (with abundant porosity and mineral inclusions). Meanwhile, granular magnetite (TD2) with oscillatory zoning, and coexisting with epidote and quartz, was precipitated from fluid with periodic variation in temperature. These oscillatory zones are characterised by bands enriched in Si, Al and Ca alternating with bands depleted in these elements. The present investigation revealed a complex evolutionary process for magnetite formation in the Duotoushan deposit. The importance of combined investigation of texture and compositional characterisation of magnetite for study of the ore genesis and evolution of Fe–Cu deposits is highlighted.

Previous accounts of pumpellyite, a blue-gree n hydrous silicate of calcium and aluminium, are few in number; the first record is that of Palache and Vassar, who described the mineral after a study of the amygdaloidal rocks of the Keweenaw Peninsula. Later Burbank recorded a very similar occurrence in Haiti, West Indies. Again, it was observed as a constituent of veins cutting glaucophaneschists in California by Irving, Vonsen, and Gonyer, and later by Waldmann at Hochlantsch Mount, Styria, in an altered diabase, and from Lake Enare, Finnish Lapland, where it occurred in altered lime-silicate rocks. Pumpellyite was found by Quitzow in diabaseporphyrites and glaueophane-rocks from the Trias of northern Calabria, Italy.

The four amphiboles described in this paper were collected during the summer of 1950 from the Sitasaongi mine. This mine, which produces high-grade manganese ore, is situated in the Chikla area, Bhandara district, India. The ore band is 8 to 18 feet thick and is strongly folded and faulted at many places (fig. 1). The most common rock types in the area are: calc-granulites, calc-gneisses, mica-schists, quartzites, gondite (quartz-spessartine-rock), injection gneisses, and pegmatites. The pegmatites are the youngest and cut through the manganese-ore band as well as the country-rocks. All are of Archaean age.

During recent years a systematic survey of the mineral resources of Ceylon has been in progress, in connexion with which a large number of specimens have been sent to the Imperial Institute for examination. In 1905 several cases containing coarse gravel from the streams of the gem-district of Balangoda were received. The constituent minerals were mainly zircon, tourmaline, corundum, spinel, ilmenite, together with small quantities of geikielite, fergusonite, and other rare-earth minerals. Last summer during the examination of these gravels one of the authors found three black crystals witll unusually brilliant faces. The apparently monoclinie form and the general physical characters at once suggested the crystallized native zirconia, baddeleyite, and this conjecture was confirmed by the goniometrical measurements and the chemical analysis.

Apparatus using cold-seal pressure vessels of molybdenum-0·5 %-titanium alloy, where each vessel is protected from oxidation by an argon gas jacket, is described. At 1000 bars pressure these vessels can be used for long runs at temperatures up to 1200° C, an increase of approximately 300° C over the range of conventional Stellite vessels. The possible use of other alloys to extend the range of this type of apparatus further is briefly discussed; pure tungsten has been shown to be too brittle.