In the southern Aosta Valley (Italian Western Alps), several massive magnetite bodies occur within serpentinized ultramafic rocks belonging to the Mesozoic meta-ophiolite nappe. The ultramafic rocks consist of lherzolite with minor dunite bodies and show a high pressure metamorphic overprint. The results of a multi-methodological study, based on optical microscopy, electron microprobe analysis and single-crystal X-ray diffraction, are reported here in order to give new insights into (1) the mineralogy and crystal chemistry of spinels and silicates and (2) the genesis of the massive magnetite bodies. Chromium-rich relict cores inside the magnetite grains suggest a derivation from primary chromite concentrations. The major-element behaviour shows the presence of two chromite types: a Cr2O3-rich (Al2O3-poor) type and a Cr2O3-poor (Al2O3-rich) type. Magnetite ore deposits probably represent the product of transformation from a chromite proto-ore which formed in ultramafic rocks pertaining to an ophiolite suite. The transformation of chromite to magnetite occurred during multiple stages: the pre- metamorphic setting of the ultramafics and the petrographic evidence suggest that metasomatism started before the onset of the alpine metamorphism and was active during the early alpine, eclogite- facies metamorphic overprint related to a subduction process under high fluid activity.

X-ray absorption spectroscopy, scanning electron microscopy (SEM) and X-ray diffractometry (XRD) have been used to study the solid-phase speciation of Zn in urban road dust sediments (RDS) in Manchester, UK. X-ray absorption near-edge structure (XANES) analysis using linear combination modelling suggest that the soluble species Zn(NO3)2·6H2O and ZnCl2 represent 70—83%, and Zn-sorbed goethite 17—30%, of the Zn species present. The presence of goethite is not corroborated by extended X-ray absorption fine structure (EXAFS) modelled first shell scattering Zn—O distances of 2.01—2.03 Å, but this may be due to distortion of the Zn octahedra on the goethite surface, or the existence of Zn-sorbed species with other metal hydrous oxides, as inferred by the EXAFS-modelled second shell Fe and Al scatterers. Analysis by EXAFS also suggests that metallic Zn-Cu-Sn-Pb and Zn-silicate phases are present in the RDS, and this is corroborated by SEM and XRD. Other phases suggested by EXAFS include ZnO, franklinite, Zn-sorbed birnessite and zinc formate. Differences between the XANES and other results suggest that model compounds such as Zn-bearing phyllosilicates and metallic Zn phases may have been missing from the XANES fitting. Long-term low-level exposure to the RDS Zn phases identified may lead to an increased risk of cardiovascular or pulmonary diseases.

Two nickel arsenates from South Terras mine, St. Stephen-in-Brannell, Cornwall, have been shown to be identical with the minerals xanthiosite and aerugite, described by C. Bergemann in 1858, and with two synthetic products described by J. B. Taylor and R. D. Heyding (1958). Xanthiosite is pure golden-yellow, monoclinic, with a 10·174, b 9·548, c 5·766 Å, β 92° 58½′, space group P21/a; with D154=5·42±0·10, the unit cell contains 4[Ni3(AsO4)2] (Dcalc 5·388±0·003). Aerugite is deep blue-green, monoclinic, with a 10·29, b 5·95, c 9·79 Å, β 110° 19′, space-group C2, Cm, or C2/m; the ideal unit cell formula is 2[Ni9As3O16], with one-sixth of the arsenic trivalent; the natural mineral has a lower Ni:As ratio, around 2·6. Both xanthiosite and aerugite are minerals new to Britain.

Early in 1947 a black, opaque, radioactive mineral resembling samarskite in appearance was discovered at Mavnzi in the Tete distrier of Mozambique, Portuguese East Africa. Two small specimens, one a rough twinned crystal with trigonal symmetry (fig. 3), were sent by h. M. Macgregor; then Director of the Geological Survey of Southern Rhodesia, to the British Museum (Natural History) for investigation, and a chemical analysis by E. Golding (table I, no. 2) followed later in the same year. X-ray photographs of fragments and powder from both specimens were taken, but revealed on development no diffraction spots, lines, or haloes. Only after prolonged heat-treatment could powder lines characteristic of crystalline material be obtained. The metamict nature of the mineral before heat-treatment is not unexpected in view of its chemical composition, optical isotropy, and glassy fracture.

X-ray diffraction refinement of the crystal structure of eosphorite has been carried out with reference to the orthorhombic space group Cmca. The structure is similar to that previously described by Hanson (1960), but the standard deviations are improved. Optical absorption and photoluminescence have also been studied for this mineral. Two sharp emission lines, denoted as R1 and R2, superimposed to a broad band (630-750 nm) have been related to the presence of Cr3+ ions. The excitation spectrum of these emissions confirms that the absorption (excitation) bands centred at 431 nm and 585 are related to with 4A2 → 4T1 and 4A2 → 4T2 spin allowed transitions of this ion.

Watanabeite Cu4(As,Sb)2S5, in which As>Sb, is a new copper sulphosalt that occurs with quartz in a hydrothermal vein at the Teine mine, Sapporo, Hokkaido, Japan. It is silvery lead-grey in colour with lead-grey streak. VHN100 = 253-306 kg/mm2, brittle. It has no cleavage and the fracture is uneven. The measured density = 4.66(2) g/cm3. The mean of six microprobe analyses gave Cu 41.1, Ag 0.1, Mn 0.3, As 15.4, Sb 14.3, Bi 2.4, S 26.2, a total of 99.8 wt.%, corresponding to: (Cu3.94Mn0.03− Ag0.01)∑3.98(As1.25Sb0.72Bi0.07)∑2.04S4.98 (basis: total atoms = 11), or ideally, Cu4(As,Sb)2S5, with As > Sb. The X-ray powder pattern resembles that of tetrahedrite but has subsidiary diffractions and is similar to that of synthetic Cu24As12S31 (Maske and Skinner, 1971). It is indexed on an orthorhombic cell with a = 14.51 Å, b = 13.30 Å, c = 17.96 Å (all ± 0.01 Å), and Z = 16. Calculated density is 4.66 g/ cm3. It is optically similar to tetrahedrite but is grey and weakly bireflectant. No internal reflections were observed. The maximum and minimum reflectance values in air and in oil (nD = 1.515) for the COM wavelengths are: 470 nm −32.5, 31.5; 17.7, 17.0, 546 nm −32.0, 31.1; 17.0, 16.3,589 nm −31.1, 30.3; 16.1 m 15.5, 650 nm −30.0, 29.3; 15.0, 14.5%, respectively. Watanabeite forms masses composed of aggregates of minute grains up to 50 μm in diameter. Apart from some minute inclusions of emplectite, native bismuth and tennantite, it is almost monominerallic.

Ktenasite from Glomsrudkollen zinc mine, Modum, Norway, is menoclinic, space group P21/c. The cell dimensions are a 5·598, b 6·121, c 23·762Å, β 95·55° The chemical formula is (Cu3·5Zn1·5)(SO4)2 (OH)6·6H2O with Z = 2; ρcale 2·96 g/cm3, ρobs 2·94 g/cm3. The mineral is biaxial negative with α (colourless) 1·574, β (bluish green) 1·615, γ (light green) 1·628, 2Vα 59°.

A new mineral, sasaite, occurs as white chalky nodules in the soil of a dolomitic cave and seems to be derived from the action of bat guano on clay minerals. Under the microscope it consists of an agglomeration of plates 10–20 µm on greatest dimension and with a rhombic shape. Its formula is (Al, Fe3+)14(PO411(OH)7SO4·83H2O and it is orthorhombic or quasi-orthorhombic. Preliminary crystallographic data based on an orthorhombic cell are a 21·50, b 30·04, c 92·06 Å, Z10, based on a calculated density of 1·747 (observed 1·75). The optical indices are α 1·465, β 1·473, γ 1·477 all ±0·001, and the principal vibration directions are parallel or quasi-parallel to the crystallographic axis.

In a recent note in this Magazine, Dr. R. B. Elliott points out that inclined contacts of grains of considerably different index may bias the result of a micrometric analysis. That there may be some bias of this sort is hardly to be doubted, though I am inclined to feel that he greatly overestimates its importance. His demonstration, however, involves a fallacy so long and widely held as to be worth refuting.

The paper opens a series devoted to the mineral diversity of the Mochalin Log rare earth element (REE) deposit, South Urals, Russia. There is a brief outline of the history of studies and geology of the deposit as well as the description of two new isostructural gatelite-group minerals, ferriperbøeite-(La) (CaLa3)(Fe3+Al2Fe2+)[Si2O7][SiO4]3O(OH)2 and perbøeite-(La) (CaLa3)(Al3Fe2+)[Si2O7][SiO4]3O(OH)2. Both minerals occur in polymineralic nodules and are associated with one another and allanite-(Ce), allanite-(La), bastnäsite-(Ce), bastnäsite-(La), ferriallanite-(Ce), ferriallanite-(La), ferriperbøeite-(Ce), perbøeite-(Ce), törnebohmite-(Ce) and törnebohmite-(La). The new minerals form isolated anhedral grains up to 0.3 mm [ferriperbøeite-(La)] and 0.5 mm [perbøeite-(La)] across and granular aggregates up to 1.5 mm × 0.5 mm [ferriperbøeite-(La)] and 3 mm × 1 mm [perbøeite-(La)]. Both minerals are brownish-black with vitreous lustre. Dcalc = 4.510 [ferriperbøeite-(La)] and 4.483 [perbøeite-(La)] g cm–3. They are optically biaxial (+); ferriperbøeite-(La): α = 1.788(5), β = 1.790(5), γ = 1.810(5) and 2Vmeas = 40(10)°; perbøeite-(La): α = 1.778(8), β = 1.783(8), γ = 1.805(8) and 2Vmeas = 40(10)°. Chemical data [wt.%, electron-microprobe; Fe3+:Fe2+ ratio from charge-balance requirements, H2O by stoichiometry; ferriperbøeite-(La)/perbøeite-(La)] are: CaO 4.91/4.81, ThO2 0.00/0.32, La2O3 23.75/22.16, Ce2O3 19.69/20.05, Pr2O3 0.85/1.09, Nd2O3 1.48/2.18, MgO 1.47/1.38, Al2O3 10.68/11.25, MnO 1.07/0.92, FeO 3.04/3.35, Fe2O3 5.31/3.78, TiO2 0.19/0.19, SiO2 27.47/27.35, F 0.11/0.23, H2O 1.61/1.54, –O = F –0.05/–0.10, total 101.58/100.50. The empirical formulae based on O20(OH,F)2 are for ferriperbøeite-(La): (Ca0.95La1.58Ce1.30Nd0.10Pr0.06)Σ3.99(Al2.27Fe3+0.72Fe2+0.46Mg0.40Mn0.16Ti0.03)Σ4.04Si4.96O20[(OH)1.94F0.06]; and for perbøeite-(La): (Ca0.94Th0.01La1.49Ce1.34Nd0.14Pr0.07)Σ3.99(Al2.42Fe3+0.52Fe2+0.51Mg0.38Mn0.14 Ti0.03)Σ4.00Si4.99O20[(OH)1.87F0.13]. Both minerals are monoclinic, P21/m; the unit-cell parameters [ferriperbøeite-(La)/perbøeite-(La)] are: a = 8.9458(2)/8.9652(4), b = 5.72971(13)/5.7306(2), c = 17.6192(3)/17.6770(9) Å, β = 115.9497(19)/116.053(6)°, V = 812.06(3)/815.88(6) Å3 and Z = 2/2. The crystal structures are solved on a single crystal and converged to R = 0.0355 [ferriperbøeite-(La)] and 0.0750 [perbøeite-(La)]. Ferriperbøeite-(La) and perbøeite-(La) are named as the La-analogues of ferriperbøeite-(Ce) and perbøeite-(Ce), respectively.

The crystal structure of new lead chloride arsenite, Pb5(As3+O3)Cl7 [orthorhombic, Pbcn, a = 16.894(2), b = 10.913 (1), c = 16.760(2) Å, V = 3090.1(7) Å3], from the historic slags of Lavrion, Greece, has been solved by direct methods and refined to R1 = 0.069. The structure contains five symmetrically unique Pb, one As, eight Cl and three O sites. The As atom forms three nearly equal As—O bonds which result in the formation of an AsO3 trigonal pyramid with As at the apex. The Pbl. Pb2, Pb3 and Pb4 atoms are bonded to the AsO3 groups via Pb2+—O bonds to form complex [Pb4(AsO3)] chains parallel to the b axis. The Pb(5) atom is coordinated solely by Cl– anions. The resulting Pb(5)Cl7 polyhedra share common edges and corners to produce bent chains parallel to the c axis. A short compilation of structural features of known lead chloride arsenites is given.

The crystal structures of two polytypes of innelite, ideally Ba4Ti2Na2M2+Ti(Si2O7)2[(SO4) (PO4)]O2[O(OH)] where M2+ = Mn, Fe2+, Mg, Ca: innelite-1T, a 5.4234(9), b 7.131(1), c 14.785(3) Å, α 98.442(4), β 94.579(3), γ 90.009(4)°, V 563.7(3) Å3, space group P1̄, Dcalc = 4.028 g/cm3, Z = 1; and innelite-2M, a 5.4206(8), b 7.125(1), c 29.314(4) Å, 0 94.698(3)°, V 1128.3(2) Å3, space group P2/c, Dcalc.= 4.024 g/cm3, Z = 2, from the Inagli massif, Yakutia, Russia, have been refined to R values of 8.99 and 7.60%, respectively. Electron-microprobe analysis gave the empirical formula for innelite as (Ba3.94Sr0.06)Σ4.00(Na2.16Mn0.382+Fe2+0.17Mg0.15Ca0.10☐0.04)Σ3(Ti2.97Nb0.02Al0.02)Σ3.01Si4.01 (S1.02P0.81☐0.17)Σ2H1.84O25.79F0.21 which is equivalent to (Ba3.94Sr0.06)Σ4.00(Ti1.97Nb0.02Al0.02)Σ2.01 [(OH0.99F0.21)Σ1.20O0.80], calculated on the basis of 26 (O + F) anions, with H2O calculated from structure refinement. The crystal structure of innelite is a combination of a TS (titanium silicate) block and an I (intermediate) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral) and exhibits linkage and stereochemistry typical for Ti-disilicate minerals of Group III (Ti = 3 a.p.f.u.): two H sheets connect to the O sheet such that two (Si2O7) groups link to the trans edges of a Ti octahedron of the O sheet. The I block contains T sites, statistically occupied by S and P, and Ba atoms. In the structures of innelite-1T and innelite-2M, TS blocks are related by an inversion centre and a cy glide plane, respectively. HRTEM images show a coherent intergrowth of the two polytypes, together with an as-yet unidentified ∼10 Å phase.

The occurrence of cookeite, a di/trioctahedral chlorite of composition (Al3.95Fe0.02Mg0.01Li0.81)(Al0.74Si3.26)O10(OH)8, in the Back Creek pyrophyllite deposit near Pambula is described. The mineral is restricted to a relatively narrow zone near the centre of the deposit and although diaspore is also present in this zone the two have not been found in intimate association, it is concluded that the introduction of lithium has been the principal factor controlling development of the cookeite.

A Th-rich mineral of the crandallite group has been investigated from the weathering profile of the Schugorsk bauxite deposit, Timan, Russia. It occurs within thin (up to 0.5 mm) organic-rich veinlets together with ‘leucoxene’ in the form of small shapeless grains which vary in size from 1—2 mm to 60—70 mm. Rare grains disseminated among boehmite crystals were also found. Microprobe analyses determined that the ThO2 content can be as high as 18 wt.%. The mineral composition is intermediate between crandallite CaAl3H(PO4)2(OH)6, goyazite SrAl3H(PO4)2(OH)6, Th-crandallite and svanbergite SrAl3PO4SO4(OH)6 in the beudantite group.

Comparatively high contents of Fe and Si and a very high positive Th and Fe content correlation (r = +0.98) suggest that the formula of the hypothetical Th-bearing end-member is ThFe3(PO4,SiO4)2(OH)6 with Th and Si substituting for REE and Prespectively (woodhouseite-type substitution). Another possible substitution is Th4+ + Ca2+ ⇋ 2REE3+ (florencite-type). A deficiency of cations in the X site can be explained by either the presence of carbon, undetectable by microprobe, in the crystal lattice or a lack of X-site cations due to radiation damage induced by Th. Some excess of cations in the B site (Al and Fe3+) can be explained by the presence of very small boehmite and hematite inclusions on the crandallite grain surfaces. Th-rich crandallite may be the result of alteration of an unidentified silicate mineral from the parent rock with a composition close to the simplified formula Fe2+ThSiO4(OH)2.

Infra-red absorption spectroscopy has been used to study the retention of hydroxyl groups by kaolinite and halloysite after heat treatment in the range 600° C. to 850° C. Structurally disordered specimens initially lose water more rapidly than do ordered specimens, but retain hydroxyl groups at higher temperatures. Work on the phases obtained above 1100° C. is incomplete, but results for the lower temperatures indicate that the ordered structures tend to retain their atomic arrangement and form metakaolin, whereas disordered structures readily rearrange to yield γ-alumina, to the formation of which water is probably essential.

Micro-FTIR (MFTIR) measurements were carried out on the natural recrystallized quartz in Ryoke granites from Mt. Takamiyama. The recrystallized quartz always shows a very strong IR absorption band at 3596 cm–1 (2.10 abs. cm–1 (normalized absorbance) under unpolarized conditions at room temperature). However, naturally deformed quartz does not show this absorption band, but only a characteristic broad band centred at 3400 cm–1. This shows that the predominant forms of H-related species in the recrystallized quartz are different from those in naturally deformed quartz. The 3596 cm–1 band is not affected by room-temperature X-ray irradiation or by annealing at temperatures of up to 600°C, and shows broadening and a positive peak shift with temperature in in situ high temperature measurements. Polarized-MFTIR measurement shows that the band has a strong polarization; the OH dipole is oriented at 35° to the a-axis in the plane and is isotropically distributed in the (0001) plane. From the stability of the band at high temperatures and against irradiation and its sharpness, the band is considered to be due to the Al(H) type point defect with no alkali which might occupy a structural position in the quartz structure.

The epicontinental sedimentary, epi- to mesozonal rocks of the Middle Palaeozoic of the Central Pyrenees host several economic Pb-Zn concentrations and numerous occurrences of these metals. The authors have endeavoured to recognize the original mineralogical nature of the epizonal host rocks in the concession of Baren (Haute-Garonne). Seventy-two whole-rock analyses were used for this purpose and interpreted by means of chemico-mineralogical diagrams.

These diagrams use parameters chosen so as to include in the projection planes the essential minerals forming the rocks under discussion. In this way, the nature and the possible initial mineralogical composition of the rocks, which are usually obliterated during metamorphism, are made visible. The chemical compositions of the different rock units are sufficiently typical to compensate for the absence of fossils and to allow stratigraphic identifications.

No volcanic contribution could be recognized in the pelites. The latter demonstrate the existence of a continent, undergoing a kaolinite-producing alteration, especially during the Silurian. The analysed trace elements (Ba, Cr, Cu, Ni, Pb, Rb, Sr, Th, U, V and Zn) are not enriched with respect to the clarkes for these rocks, except slightly in the case of U and Th and more strongly for Cr and V. The carbonate rocks contain predominantly calcite, with subordinate dolomite. They show a strong enrichment in Ba, whereas the content of the other trace elements is normal.