Hexaferrum, defined as an hcp Fe mineral containing varying amounts of Ru, Os, or Ir (Mochalov et al. 1998) was re-examined in the light of new analyses of similar alloys from the Loma Peguera and Loma Larga chromitites, in the central part of Loma Caribe peridotite, Cordillera Central of the Dominican Republic, together with a review of the phase chemistry in the Fe–Ni–Ir and Fe–Ru–Ir systems. We conclude that the hcp (Fe,Ir) mineral corresponds to the ε-phase of Raub et al. (1964) and should be differentiated from hexaferrum [(Fe,Os) and (Fe,Ru)] because it is separated by one to two miscibility gaps and therefore is not a continuous solid solution with Fe.

Since W. Lindgren first detected the presence of microphenocrysts of analcime in basalt, many observers have recorded this mineral as a constituent of igneous rocks, but there is some difficulty in distinguishing between analcime and glass and between analcime and leucite in thin rock-sections. For instance, H. Rosenbusch identified the interstitial colourless isotropic material in monchiquites as glass, whereas L. V. Pirsson showed it to be analcime. H.S. Washington showed that basalts from Sardinia, previously thought to be leueitic, contain phenocrysts of analcime. A. Lacroix also found, in his study of north African basaltic lavas, that in many cases so-called leucite-lavas actually contain analcime and not leucite.

A new phyllosilicate mineral, lipuite (IMA2014-085), has been discovered from the N'Chwaning III mine, Kalahari Manganese Fields, Northern Cape Province, Republic of South Africa. It occurs as platy, tabular, or granular crystals and veined agglomerate in association with Mn-bearing sugilite, taniajacoite, pectolite, richterite, norrishite and namansilite. Lipuite is dark red–brown with vitreous lustre, red streak, an estimated Mohs hardness of 5 and the measured density is 2.83(3) g/cm3. It is biaxial (+) and characterised by bright red to dark red colour in thin section with measured refractive indices in white light: α = 1.635(1), β = 1.653(1), γ = 1.670(1) and 2V = 86(2)°. The Raman spectra of lipuite are composed of over 21 bands at 109, 146, 162, 183, 206, 244, 288, 342, 362, 455, 496, 520, 552, 613, 669, 886, 930, 971, 1097, 3487 and 3540 cm–1. The empirical formula from microprobe analyses is (based on total number of cations = 27.5 and structural refinement): K1.12Na8.16(Mn4.77Fe0.07)Σ4.84Mg0.44[Si11.97O30(OH)4](PO4)0.94O2(OH)2·4H2O. The idealised formula is: KNa8Mn3+5Mg0.5[Si12O30(OH)4](PO4)O2(OH)2·4H2O.

Lipuite is orthorhombic, space group Pnnm, a = 9.080(3), b = 12.222(3), c = 17.093(5) Å, V = 1897.0(9) Å3 and Z = 2. The strongest powder X-ray diffraction peaks [d, Å (I) (hkl)] are: 9.965(40)(011), 2.938(33)(310), 2.895(100)(311), 2.777(38)(224), 2.713(53)(320), 2.483(32)(126), 2.086(35)(046) and 1.534(40)(446). The crystal structure of lipuite is characterised by sheets of SiO4 tetrahedra that are linked together along [010] by K+, Na+, Mn3+, Mg2+ and P5+ cations, as well as hydrogen bonds. These tetrahedral sheets consist of 14-membered rings of SiO4 tetrahedra that zigzag along [100]. The two independent Mn3+ cations are both octahedrally coordinated. They form five-membered, edge-shared octahedral clusters between the SiO4 tetrahedral sheets. Lipuite represents a rather unique structure type and its silicate tetrahedral sheets can be considered a derivative of the silicate sheets in mica.

The Ve Skerries form a small group of rocks situated just over three miles WNW. of Papa Stour on the west coast of the Shetland Isles. Owing to the notoriously troubled state of the surrounding waters a landing can only rarely be ettected on them, and it is not, therefore, surprising that no account of their geology has yet appeared. Through the kindness of Mr. J. Glencorse Wakelin, Secretary to the Northern Lights Commissioners, the writer has been able to examine a large specimen of the constituent rock secured by Mr. Wakelin in 1930, and considered by him to be typical of the group. The results of this examination proved to be of considerable interest and are given below.

In the hand-specimen the rock is seen to be of even texture and medium grain. It is white in colour but is relieved by a few darkgreen or black spots and by very thin veins of haematite. In appearance it is not unlike an aplogranite, but examination under a handlens reveals the absence of quartz, while much of the felspar is seen to be twinned on the albite-law.

We report an unusual occurrence of margarite, corundum, gahnite and zincohögbomite from the Raleigh terrane in the Piedmont Province of Virginia. The assemblage occurs in a chlorite-rich blackwall associated with a small metamorphosed ultramafic rock body. The blackwall is dominated by chlorite, but also contains distinctive clusters (1–4 mm across) that typically consist of ragged Zn-rich spinel grains surrounded by masses of randomly oriented margarite. Also spatially associated with spinel are smaller grains of corundum and högbomite. In most cases, spinel and högbomite are sufficiently enriched in Zn to be called gahnite and zincohögbomite, respectively. Some högbomite grains are distinctly banded in back-scattered electron images, primarily reflecting variations in Zn-content. Textures suggest that högbomite formed at the expense of spinel (although locally the reverse relationship holds), and högbomite compositions mimic those of spinel. Margarite appears to be a later phase, and textures imply formation via reactions with spinel, corundum and, possibly, chlorite. This occurrence of Zn-rich spinel and högbomite is clearly related to the bulk composition of the blackwall rock, which contains >2500 ppm Zn. The origin of this Zn-rich composition is unclear, but could be due to a small amount of sphalerite or zincian-staurolite in the protolith.

The crystal structure of hejtmanite, Ba2Mn4Ti2(Si2O7)2O2(OH)2F2, from Mbolve Hill, Mkushi River area, Central Province, Zambia (holotype material) has been refined on a twinned crystal to R 1 = 1.88% on the basis of 4539 [|F| > 4|F|] reflections. Hejtmanite is triclinic, C1̅, a = 10.716(2), b = 13.795(3), c = 11.778 (2) ,= 90.07(3),= 112.24(3),= 90.03(3), V = 1612(2) 3. Chemical analysis (electron microprobe) gives: Ta2O5 0.09, Nb2O5 1.27, ZrO2 0.65, TiO2 14.35, SiO2 23.13, BaO 26.68, SrO 0.19, FeO 11.28, MnO 15.12, Cs2O 0.05, K2O 0.33, F 3.82, H2Ocalc. 1.63, O = F 1.61, total 97.10 wt.%, where the H2O content was calculated from the crystal-structure refinement, with (OHF) = 4 apfu. The empirical formula, calculated on the basis of 20 (OF) anions, is of the form (Si2O7)2(XO)4(XP)2, Z=4: (Ba1.82K0.07 Sr0.02)Σ1.91(Mn2.33 Zr0.04Mg0.03)Σ3.95(Ti1.88Nb0.10Zr0.02)Σ2(Si2.02O7)2O2[(OH)1.89 F0.11]Σ2F2. The crystal structure is a combination of a TS (Titanium Silicate) block and an I (intermediate) block. The TS block consists of HOH sheets (Hheteropolyhedral, Ooctahedral). The topology of the TS block is as in Group-II TS-block minerals: Ti ( Nb) = 2 apfu per (Si2O7)2 [as defined by Sokolova (2006)]. In the O sheet, five [6]MO sites are occupied mainly by Mn, less Fe2 and minor Zr and Mg, with <MOφ> = 2.198(φ = O,OH), ideally giving Mn4 apfu. In the H sheet, two [6]MH sites are occupied mainly by Ti, with <MHφ> = 1.962(φ = O,F), ideally giving Ti2 apfu; four [4] Si sites are occupied by Si, with < SiO> = 1.625 . The MH octahedra and Si2O7 groups constitute the H sheet. The two [12]Ba-dominant AP(1,2) sites, with <APφ> = 2.984(φ = O, F), ideally give Ba2 apfu. Two (1,2) and two (1,2) sites are occupied by O atoms and OH groups with minor F, respectively, ideally giving (XO)4 = ()2()2=O2(OH)2 pfu. Two (1,2) sites are occupied by F, giving F2 apfu. TS blocks link via a layer of Ba atoms which constitute the I block. Simplified and end-member formulae of hejtmanite are Ba2(Mn,Fe2)4Ti2 (Si2O7)2O2(OH,F)2 F2 and Ba2Mn4Ti2(Si2O7)2O2(OH)2F2, Z = 4. Hejtmanite is a Mn-analogue of bafertisite, Ba2 4 Ti2(Si2O7)2O2(OH)2F2.

The theory of a new method for the determination of reflectivity at truly normal incidence is described. A parallel light beam falls on the specimen after passing through a glass cube with semi-silvered diagonal mounted at the centre of an optical goniometer. The various reflected beams are measured by a photomultiplier fixed to the telescope of the goniometer. Experiment has proved the validity of the method and the spectral reflectivity of pyrite in air and in oil has been investigated.

The Ergheo meteorite was inspected both by transmitted and reflected light in order to look for evidence of shock metamorphism by petrological observations. The stone is a well-recrystallized olivine-hypersthene chondrite that shows features of severe fracturing, prominent veining, and diffused cracking. The presence of several shock-transformed components is described in some detail. Ergheo is a meteorite that suffered particularly by shock in full agreement with Heymann's (1967) and Turner's (1968) statements.

In the absence of published experimental data on phase equilibria in the ternary system Fe-Sb-S and on the stability relations of gudmundite (FeSbS) and berthierite (FeSb2S4) , some preliminary investigations on the upper stability limit of natural gudmundite are briefly described. On heating in vacuo, As-free gudmundite broke down between 269° and 288°C, an approximate upper stability limit of 280±10°C conforming to the stability relations of the associated phases.

A new hydrated zinc aluminium phosphate mineral has the composition ZnAl2(PO4)2(OH)2.3H2O. It has been named kleemanite. It occurred rarely both as veinlets 1–2 mm thick, and as thin layers on surfaces of cracks and small cavities in one section of the iron ore deposit at Iron Knob, South Australia. Chemical, X-ray, thermal analysis, and optical data are given.

The Environment Agency Guidance on Requirements for Authorisation (GRA) of a geological disposal facility (GDF) requires a demonstration that "the possibility of a local accumulation of fissile material such as to produce a neutron chain reaction is not a significant concern." A neutron chain reaction that is just self-sustaining is also known as critical.

Waste packages can be designed to ensure that criticality is impossible during the transport and operational phases of a GDF, and for a significant period post-closure. Over longer times, however, packages may degrade, and groundwater flows could lead to a localized accumulation of fissile material. Hence, even though the initial distribution of materials would need to change substantially, criticality cannot be ruled out completely.

This paper describes how an accumulation of fissile material could, hypothetically, lead to a critical configuration; how such a system could evolve; what the local consequences could be; and how the engineered and geological barriers could be affected. The conclusion from studies to date is that, even for large (and very unlikely) fissile accumulations, the consequences of a post-closure criticality event are not a significant concern.

Natropalermoite, ideally Na2SrAl4(PO4)4(OH)4, the Na-analogue of palermoite, is a new mineral from the Palermo No. 1 mine, Groton, New Hampshire, USA. Associated minerals are palermoite, eosphorite and quartz. Natropalermoite crystal sare prismatic with striations parallel to the direction of elongation (the a axis) up to 200 μm × 50 μm × 45 μm in size. The mineral is colourless, transparent with a white streak and vitreous lustre and is visually indistinguishable from palermoite. It is brittle with subconchoidal fracture and has a Mohs hardness of 5.5. Cleavage is perfect on {001}, fair on {100} and no parting was observed. The calculated density is 3.502 g cm–3. Natropalermoite is biaxial (–), α = 1.624(1), β = 1.641(1), γ = 1.643(1) (589nm), 2Vmeas = 43(4)°, 2Vcalc = 38°. An electron microprobe analysis yielded an empirical formula (based on 20 O apfu) of (Na1.69Li0.31)∑2.00(Sr0.95Mg0.04Ca0.02Ba0.01)∑1.02(Al3.82Mn0.03Fe0.03)∑3.88(P1.01O4)4(OH)4.

Natropalermoite is orthorhombic, space group Imcb, a = 11.4849(6), b = 16.2490(7), c = 7.2927(4) Å, V = 1360.95(17) Å3, Z = 4. Natropalermoite is isotypic with palermoite, but substitution of the larger Na for Li results in substantial increase of the b cell parameter. Four of the seven Na–O distances are longer than their equivalents in palermoite, resulting in a more regular 7-fold coordination polyhedron about Na. The eight strongest peaks in the calculated X-ray powder diffraction are [dcalc(Å),Irel%, (hkl)]: [3.128, 100, (321)], [4.907, 68, (121)], [3.327, 48, (022)], [4.689, 45, (220)], [3.078, 45, (202)], [2.453, 38, (242)], [2.636, 35, (411)], [2.174, 35, (422)].

The diffusivity and diffusion mechanisms of hydrogen together with with deuterium and lithium, parallel to the c axis of quartz, were investigated experimentally at 800°C, 0.1 GPa with the activity of H2O or 2H2O ≈ 1 [2H is used throughout this work to describe deuterium rather than D, to avoid confusion with the diffusion coefficient, D]. The pH was set using mixtures of H2O (or 2H2O) and HCl. Three types of experiment were conducted: (1) H-in/Li-out; (2) 2H-in/H-out; and (3) 2H-in/H + Li out, using three different natural quartz crystals as starting materials. Profiles of H, 2H and Li were measured using Fourier-transform infrared (FTIR) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). H, 2H and Li are charge-compensated by Al3+ replacing Si4+, or by excess O2–. The total atomic concentration of monovalent cations appears to remain constant over the duration of the experiments. The resulting diffusion profiles are different for the three experimental designs and three starting materials, and some show complex shapes inconsistent with simple diffusion. A multi-site diffusion–reaction model is developed, with the theory based on previous models that have been derived mainly on the basis of conductivity measurements. In these models, the monovalent cations move away from their charge-balancing ion then diffuse rapidly to another site. The mobility of the monovalent cations is described by both a diffusion coefficient and an equilibrium constant that enables dissociation of the immobile charge-balanced defects. This model can describe complex step-shaped profiles formed in H-in/Li-out experiments, profiles with local maxima ('humped’ profiles) in 2H-in/H + Li out experiments, and error function-shaped profiles in 2H-in/H-out and previously published Li-in/H-out experiments. Our data provide support for models previously proposed for quartz. Studies of the lengths and forms of diffusion profiles from such experiments provide a useful complement to assertions from conductivity experiments.

Epididymite, determined by means of its optical properties, X-ray powder pattern, and spectrographic analysis, was found in a desilicated pegmatite near Věžná, Western Moravia, Czechoslovakia. It was formed contemporaneously with minor amounts of milarite in a late hydrothermal stage by the action of sodium-rich solutions on beryl. This is the first occurrence of epididymite and milarite as alteration products of beryl and the first findings of epididymite in any other paragenesis than that of alkaline pegmatites. The optical properties of epididymite are re-examined and older data rejected.

Relianceite-(K), K4Mg(V4+O)2(C2O4)(PO3OH)4(H2O)10, is a new mineral species from the Rowley mine, Maricopa County, Arizona, USA. It occurs in an unusual bat-guano-related, post-mining assemblage of phases. Other secondary minerals associated with relianceite-(K) are antipinite, dendoraite-(NH4), fluorite, mimetite, mottramite, rowleyite, salammoniac, struvite, vanadinite, willemite, wulfenite and at least one other new mineral. Crystals of relianceite-(K) are sky blue prisms up to ~0.1 mm in length. The streak is very pale blue and lustre is vitreous, Mohs hardness is 2½, tenacity is brittle and fracture is splintery. The calculated density is 2.111 g⋅cm–3. Relianceite-(K) is optically biaxial (+) with α = 1.528(2), β = 1.529(2), γ = 1.562(2) (white light); 2Vmeas = 22(1)°; orientation Z = b; pleochroism: X = colourless, Y = pale blue, Z = pale blue; X < Y ≈ Z. Electron microprobe analysis gave the empirical formula [K2.21(NH4)1.79]Σ4.00Mg0.96(V4+0.95O)2(C2O4)[P1.03O3.03(OH)0.97]4(H2O)10, with the C, N and H contents constrained by the crystal structure. Raman spectroscopy confirmed the presence of NH4 and C2O4. Relianceite-(K) is monoclinic, Pc, with a = 12.404 (7) Å, b = 9.014 (6), c = 13.260 (8) Å, β = 100.803(10)°, V = 1456 (2) Å3 and Z = 2. The structural unit in the crystal structure of relianceite-(K) (R1 = 0.0540 for 3751 Io > 2σI reflections) is a (V4+O)2(C2O4)(PO3OH)4 chain in which VO6 octahedra are bridged by an oxalate group to form [V2C2O12] dimers, PO3OH tetrahedra form a double bridge between the VO6 octahedra of the dimers, and additional PO3OH tetrahedra decorate the chain. Topologically, this is the same chain found in the structure of davidbrownite-(NH4). The MgO(H2O)5 octahedron can be considered a distant decoration on the chain. The chains are linked to each other through an extensive system of K/NH4–O bonds and hydrogen bonds.

Authigenic envelopes up to 0·18 mm thick on clastic potassium feldspar grains from arkoses and subgreywackes of the Devonian Nannyarra Greywacke have been examined with the four-axis universal stage. The plane of the optic axes is parallel to (010) in some segments of individual envelopes and normal to (010) in others, and the range of 2Vα over all envelopes is from close to 0° to 65°. The optics are ascribed to modifications of potassium feldspar corresponding to high-and low-sanidine and orthoclase.

Cross-hatched twinning is characteristic of two alkali-felspar species, microclines and anorthoclases. Because of the difference in the crystallographic angles of these two species, the cross-hatched twinning is most clearly seen in (001) sections of microcline and in sections perpendicular to the a crystallographic axis in anorthoclases. If pericline twinning is present it is generally seen in (010) sections of microclines, but if the microcline is microperthitic the twin lamellae may not be seen. Strings or lamellae of perthitic albite can be distinguished from pericline twin lamellae by refractive index differences and also by the angle that their trace makes with the trace of (001) in (010) sections.

A Visual Basic program (TOURCOMP) has been written to recast the tourmaline composition into end-member components from electron microprobe data or more complete tourmaline analyses. TOURCOMP is a program based on a linear algebraic model that directly calculates the end-member proportions of tourmalines from their structural formulae. The program is developed for IBM-compatible personal computers running under the Windows™ operating system. The source code has been also translated and compiled in order to run on an Apple computer. Analytical problems, uncertainties concerning site occupancies, and the normalization procedure to determine the structural formula are the main error sources. However, the method of recalculating tourmaline end-members presented in this paper is considered to provide reasonably good results, bearing in mind the chemical complexity of tourmaline.