The technique of X-ray absorption microspectroscopy is described, with particular reference to the determination of calcium in a hydrogel formed in minute amounts in cavities in larnite. The method, which is applicable to other elements, enables chemical data to be obtained from selected small areas in a normal petrological thin section.

The new alluaudite-group mineral badalovite was found in the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with hematite, tenorite, cassiterite, johillerite, nickenichite, calciojohillerite, bradaczekite, metathénardite, aphthitalite, langbeinite, calciolangbeinite, sanidine, fluorophlogopite, fluoborite, tilasite, anhydrite, pseudobrookite, sylvite, halite, lammerite, urusovite, ericlaxmanite, arsmirandite, svabite, krasheninnikovite, euchlorine, wulffite and alumoklyuchevskite. Badalovite forms oblique-angled prismatic crystals up to 1 mm × 1 mm × 5 mm, typically combined in groups or crusts up to several hundred cm2 in area. The mineral is transparent, green, grey, yellow or colourless, with vitreous lustre. It is brittle, the Mohs hardness is 3½. Cleavage was not observed, the fracture is uneven. Dcalc is 4.02 g cm–3. Badalovite is optically biaxial (–), α = 1.753(3), β = 1.757(3), γ = 1.758(3) and 2Vmeas. = 50(10)°. Chemical composition (wt.%, electron-microprobe; holotype) is: Na2O 9.23, K2O 0.19, CaO 2.04, MgO 13.78, MnO 0.31, CuO 0.12, ZnO 0.24, Al2O3 0.06, Fe2O3 12.77, TiO2 0.01, SiO2 0.06, P2O5 0.33, V2O5 0.05, As2O5 61.51, SO3 0.02, total 100.72. The empirical formula based on 12 O apfu is Na1.67Ca0.20K0.02Mg1.92Zn0.02Mn0.02Cu0.01Fe3+0.90Al0.01(As3.01P0.03Si0.01)Σ3.05O12. The simplified formula is Na2Mg2Fe3+(AsO4)3. Badalovite is monoclinic, C2/c, a = 11.9034(3), b = 12.7832(2), c = 6.66340(16) Å, β = 112.523(3)°, V = 936.59(4) Å3 and Z = 4. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are: 6.41(38)(020), 5.505(20)(200), 3.577(23)($\bar{1}$31), 3.523(25)(310), 3.211(46)($\bar{1}$12), 2.911(28)($\bar{2}$22, $\bar{3}$12), 2.765(100)(240, 400) and 2.618(26)($\bar{1}$32). The crystal structure was solved from single-crystal XRD data with an R1 of = 2.49%. Badalovite is isostructural with other alluaudite-group minerals. Its simplified crystal chemical formula is A(1)NaA(1)’□A(2) □A(2)’NaM(1)MgM(2)(Mg0.5Fe3+0.5)2(AsO4)3 (□ – vacancy) and the end-member formula is NaNaMg(MgFe3+)(AsO4)3. The mineral is named in honour of the outstanding mineralogist and geochemist Stepan Tigranovich Badalov (1919–2014).

Two new occurrences of the lead oxy-sulfosalt chovanite have been identified at the Monte Arsiccio and Pollone mines, Apuan Alps, Tuscany, Italy. Chovanite from Monte Arsiccio occurs as black acicular crystals, up to 5 mm long, associated with rouxelite, robinsonite, sphalerite, valentinite,baryte, dolomite, quartz and Ba-rich K-feldspar ('hyalophane') in metadolostone vugs. Its unit-cell parameters are a = 48.38(5), b = 4.11(4), c = 34.18(4) Å, β = 106.26(2)°, V = 6521(64) Å3, space group C2/m. Very weakreflections indicate the doubling of the b parameter. Electron-microprobe data gave (wt.%): Ag 0.28, Tl 1.51, Pb 45.57, Sb 31.00, As 1.09, S 19.73, Se 0.05, Cl 0.02, sum 99.25. On the basis of ∑Me = 58 apfu, its formula is Ag0.30Tl0.86Pb25.56Sb29.59As1.69S71.52Se0.07Cl0.05.Adding one oxygen atom, it is close to the formula TlPb26(Sb,As)31S72O. Chovanite from Pollone occurs as thick black acicular crystals, up to 1 cm long, associated with baryte and quartz. The high-diffraction quality of the available material allowed the solutionand refinement of the 8 Å crystal structure in the space group P21/c, with unit-cell parameters a = 34.052(3), b = 8.2027(7), c = 48.078(4) Å, β = 106.258(4)°, V = 12891.9(19) Å3. The refinement convergedto R1 = 9.14% on the basis of 19,853 observed reflections with Fo > 4σ(Fo). Electron-microprobe data gave (wt.%): Ag 0.12, Tl 0.54, Pb 48.34, Bi 0.20, Sb 26.71, As 3.37, S 20.23, Cl 0.07, sum 99.57. It corresponds to the formulaAg0.13Tl0.30Pb26.94Bi0.10Sb25.33As5.20S72.85Cl0.20, close to the idealized formula Pb28(Sb,As)30S72O, with a single oxygen atom bound to two (Sb/As) atoms alternating witha vacancy along b as in scainiite and in other Pb oxy-sulfosalts. The crystal chemistry of this 8 Å crystal structure is detailed, taking into account its modular description, the (Sb,As)mSn polymerization, its topological derivation from pellouxite,and the oxygen non-stoichiometry.

Fluorine-rich prismatine, (□,Fe,Mg)(Mg,Al,Fe)5Al4(Si,B,Al)5O21(OH,F), with F/(OH+F) = 0.36–0.40 and hercynite are major constituents of a Fe-Al-B-rich lens in ultrahigh-temperature granulite-facies quartz-sillimanite-hypersthene-cordierite gneisses of the Eastern Ghats belt, Andhra Pradesh, India. Hemo-ilmenite, sapphirine, magnetite, biotite and sillimanite are subordinate. Lithium, Be and B are concentrated in prismatine (140 ppm Li, 170 ppm Be, and 2.8 –3.0 wt.% B2O3). Another Fe-rich lens is dominantly magnetite, which encloses fine-grained zincian ferrohögbomite-2N2S, (Fe2+,Mg,Zn,Al)6 (Al,Fe3+,Ti)16O30(OH)2, containing minor Ga2O3 (0.30 –0.92 wt.%). Fe-Al-B-rich lenses with prismatine (or kornerupine) constitute a distinctive type of B-enrichment in granulite-facies rocks and have been reported from four other localities worldwide. A scenario involving a tourmalineenriched lateritic precursor affected by dehydration melting is our preferred explanation for the origin of the Fe-Al-B-rich lenses at the five localities. Whole-rock analyses and field relationships at another of these localities, Bok se Puts, Namaqualand, South Africa, are consistent with this scenario. Under granulite-facies conditions, tourmaline would have broken down to give kornerupine-prismatine (±other borosilicates) plus a sodic melt containing H2O and B. Removal of this melt depleted the rock in Na and B, but the formation of ferromagnesian borosilicate phases in the restite prevented total loss of B.

Basement rocks of Santorini have been locally impregnated by iron oxides and other minerals. The hydrothermal fluids which caused the mineralization have extensively altered the impregnated rocks, but left granditic garnets in these unaffected.

Mössbauer spectroscopy and differential X-ray diffraction show that the iron oxides present are goethite and hematite in a ratio of about 2 : 1. The presence of hematite indicates that these minerals formed, directly from a hydrothermal phase, at higher temperatures than the recent submarine iron oxide deposits of Santorini, which contain no hematite.

The conclusion of Zaffiro et al. (2019; Constraints on the Equations of State of stiff anisotropic minerals: rutile, and the implications for rutile elastic barometry. Mineralogical Magazine, 83, 339–347) that the Mie–Grüneisen–Debye (MGD) Equation of State (EoS) cannot fit the available data for rutile is shown to be incorrect, even though rutile exhibits significant anisotropic thermal pressure which invalidates the quasi-harmonic approximation used as the basis for the MGD EoS. The refined parameters for the MGD EoS of rutile are: KTR0= 205.05(25) GPa, $K_{TR0}^{\prime} $ = 7.2(5), θD = 399(20) K, γ0= 1.40(2) and q = 1.5(7). This EoS predicts volumes, bulk moduli and volume thermal expansion coefficients for rutile at metamorphic conditions that are statistically indistinguishable from those predicted by the ‘isothermal’ type of EoS reported previously.

Over 100 samples of ‘pegmatite’ and associated host rocks from the Cree Lake Zone of northern Saskatchewan have been studied. The degree of U and Th enrichment of the pegmatites appears to depend on the parent material of the anatectic melts produced during the Hudsonian thermotectonic event. Evidence for Archaean granulite-facies depletion of U and Th is inconclusive; however, important enrichment of U and Th in the basal Aphebian is associated with metamorphosed black shales and possibly evaporates.

The crystal structure of kraisslite, orthorhombic (pseudo-hexagonal), a = 8.1821(1), b = 14.1946(3), c = 43.9103(8) Å, V = 5099.8(2) Å3, Z = 4 and d calc = 4.083 g cm–3, has been solved bydirect methods and refined in the space group C2221 to an R 1 index of 1.68% for 7432 observed (|F o| > 4σ|F|) reflections. Electron-microprobe analysis gave the following chemical composition: As2O510.86,As2O36.18, SiO213.39, Al2O30.25, Fe2O32.06, MnO 51.14, ZnO 7.39, MgO 2.13, CaO 0.05, H2Ocalc = 4.50, sum 97.95 wt.%; and empirical formula: Zn2.91(Mn23.07Mg1.69Ca0.03)Σ=24.79(Fe0.83 3+Al0.16)Σ=0.99(As3+O3)2[(Si0.71As0.30 5+)O4]10(OH)16 calculated on the basis of 62 anions with (OH) = 16 and As3+/(As3++ As5+) taken from the refined crystal structure. The general formula, [4]Zn3(Mn,Mg)25(Fe3+,Al)(As3+O3)2[(Si,As5+)O4]10(OH)16, differs from those given previously.

There is one As3+ site with a <As–O> distance of 1.780 Å and a stereochemistry typical of a stereoactive lone-pair of electrons. There are five tetrahedrally coordinated T sites with <T–O> distances from 1.635 to 1.692 Å; the T(1)site is fully occupied by As5+, and the T(2)–T(5) sites are occupied by both Si and As5+. There are two tetrahedrally coordinated Zn sites with <T–O> distances of ∼1.996 Å, both of which are occupied by dominantZn and minor Mn2+. There are thirteen octahedrally coordinated M sites, twelve of which are occupied by dominant Mn2+ with lesser Mg and minor Zn; <M–O> distances are in the range 2.197–2.284 Å. The <M(13)–O> distanceis 2.083 Å and its lower site scattering indicates occupancy by Fe3+, Mn2+, Mg and Al. The structure consists of five crystallographically distinct layers of polyhedra, labelled m = 0 – 4. Layer m = 0 consists of corner-sharing Zn and (Si, As5+)tetrahedra, and layers m = 1–4 each consist of trimers of Mn2+ octahedra linked by (Si, As5+) tetrahedra and intrasheet hydrogen bonds (m = 1, 3) or (Si, As5+) tetrahedra and (Fe3+,Al) octahedra (m = 2) or (As5+)tetrahedra and (As3+O3) triangular pyramids and intrasheet hydrogen bonds (m = 4). The layers stack along [001] with reversals of the sequence m = 1, 2, 3, 4 at z = 0, ¼, ½ and ¾. Kraisslite is a member of the mcgovernite family.

Grandidierite has been found in hornfelses around a diorite stock on Cuvier Island. Physical properties and electron microprobe analyses are given for two Cuvier Island and two Madagascan grandidierites. The Cuvier Island grandidierite has crystallized under conditions of the K-feldspar-cordierite hornfels facies at temperatures of approximately 600°C. and pressures (Pload) of less than 300 bars.

The thermal disintegration of crocidolite has been investigated with X-ray powder and rotation photographs. Initial disintegration products include monoclinic pyroxene, iron oxide phases, and eristobalite as a pseudomorph of the original fibre bundles but at about 1000° C fusion occurs due to incongruent melting of the pyroxene. The products are strongly oriented along the fibre axis and full orientation relationships have been deduced with the aid of structural models. From these relationships it is suggested that regions of the amphibole structure on (100) are retained in the product phases without change in orientation.

Deep azure-blue beryl is reported from veins in Upper Devonian conglomerate from southeast Ireland. Microprobe analysis, Mössbauer spectroscopy and loss on ignition suggest an unusual chemistry with an exceptionally high degree of substitution of Fe and Mg for Al, and extreme amounts of Na and water held within channel sites in the structure. The calculated structural formula is:

Refractive indices (1.603 and 1.595) and the cell edge, a, (9.292 Å) are also unusually high. Colourless beryl from the same locality, some of which forms cores to blue beryl prisms, has less octahedral substitution and a lower Fe/Mg ratio. The origin of the beryl is tentatively linked to contemporaneous volcanic activity.

Jeppeite, a new mineral, similar in composition to and overgrown on priderite, has been found in the lamproite plug of Walgidee Hills (18° 19′ S, 124° 51′ E), Western Australia. The mineral is named for the discoverer, Dr J. Jeppe. It is monoclinic, C2/m, a 15.453 b 3.8368 c 9.123 Å β 99.25°, strongest powder lines 4.50(002) (4), 3.07(310) (10), 2.99(003,31) (10), 2.961(20) (4), 2.812(311,112) (10), 2.091 (6), 2.074 (6), 1.919 (8) similar to artificial K2Ti6O13. The sparse eluvial crystals are black, elongated along b, bounded by {100}, {20} faces (Λ 45°) and {010}; perfect 100 and good 20 cleavages or partings, submetallic lustre, pale-brown streak, brittle, and cleave into (100) flakes. Dobs 3.94, Dcalc 3.98. Colour values for illuminant C from reflectance spectra for Rp, Rb, and Rθ are: Y% 13.3, 14.4, 16.6; λd 474, 473, 475; and Pe% 5.1, 4.5, 4.3. Refractive indices from reflectances at 590 nm in air are 2.13, 2.21 and 2.35. In thin section, αΛα10° blue, β = b dark greenish brown almost to black, γ = c brown. Bireflectance and birefringence positive. H 5–6, VHN100 orientation dependent; for indentations normal to b 664–773.

Jeppeite is common in the lamproite as prismatic to acicular aggregates associated with priderite, richterite, shcherbakovite, wadeite, perovskite, and apatite in a green and white celadonite and chlorite matrix, with a little calcite and sphene, after olivine, pyroxene, and leucite.

Electron probe analysis, using Fe, Ti, nepheline, and benitoite standards, gave K2O 8.47, BaO 17.35, TiO2 69.29, Fe2O3 (total Fe) 4.74, sum 99.85%; (Mg, Na, Zr detected). This analysis calculates to (K1.15,Ba0.73)Σ1.88 (Ti5.56, Fe3+0.38)Σ5.94O13, or ideally, (K,Ba)2(Ti,Fe)6O13.

Aluminium-bearing strunzite, [Mn0.65Fe0.26Zn0.08Mg0.01]2+[Fe1.50Al0.50]3+(PO4)2(OH)2·6H2O, occurs as fibrous aggregates in a crystallographically oriented association with jahnsite on altered zwieselite samples from the phosphate pegmatite at Hagendorf Süd, Bavaria, Germany. Synchrotron X-ray data were collected from a 3 μm diameter fibre and refined in space group P to R1 = 0.054 for 1484 observed reflections. The refinement confirmed the results of chemical analyses which showed that one quarter of the trivalent iron in the strunzite crystals is replaced by aluminium. The paragenesis revealed by scanning electron microscopy, in combination with chemical analyses and a crystal-chemical comparison of the strunzite and jahnsite structures, are consistent with strunzite being formed from jahnsite by selective leaching of (100) metal—phosphate layers containing large divalent Ca and Mn atoms.

Sectored vesuvianite showing optically triclinic properties was studied by X-ray and P-FTIR analyses, and the origins of the internal optical texture are discussed. A monoclinic refinement (space group P2/n) suggests that site occupancies are slightly different among the Al(2) series, though the OH– dipole is randomly oriented in all sectors. A relationship between the surface and internal texture suggests that these sectoral structures were produced during crystal growth, not by phase transitions.

Experiments in the system NaAlSiO4(Ne)−KAlSiO4(Ks)−SiO2(Qz)−H2O at 100 MPa show that the maximum content of NaAlSi2O6 in leucite is ∼4 wt.% and that analcime is close to the stoichiometric composition (NaAlSi2O6.H2O). Analcime forms metastably on quenching the higher-temperature experiments; it is secondary after leucite in experiments quenched from 780°C, while from 850°C it forms by alteration of leucite, and by devitrification of water-saturated glass. Both processes involve reaction with Na-rich aqueous fluids. Stable analcime forms at 500°C, well below the solidus, and cannot form as phenocrysts in shallow volcanic systems. New data for natural analcime macrocrysts in blairmorites are presented for the Crowsnest volcanics, Alberta, Canada. Other researchers have suggested that primary analcime occurs as yellow-brown, glassy, analcime phenocrysts. Our microprobe analyses show that such primary analcime is close to stoichiometric, with very low K2O (<0.1 wt.%), minor Fe2O3 (0.5−0.8 wt.%) and CaO (∼0.5 wt.%). An extrapolation of published experimental data for Ne−Ks−Qz at >500 MPa PH2O, where Anl + melt coexist, suggests that at >800 MPa two invariant points are present: (1) a reaction point involving Kf + Ab + Anl + melt + vapour; and (2) a eutectic with Kf + Anl + Ne + melt + vapour. We suggest that the nepheline-free equilibrium mineral assemblage for Crowsnest samples is controlled by reaction point (1). In contrast, blairmorites from Lupata Gorge, Mozambique, form at eutectic (2), consistent with the presence of nepheline phenocrysts. Our conclusions, based on high- vs. low-pressure experiments, confirm the suggestion made by other authors, that Crowsnest volcanic rocks must have been erupted explosively to preserve glassy analcime phenocrysts during very rapid, upward transport from deep in the crust (H2O pressures ≫500 MPa). Only rare examples survived the deuteric and hydrothermal alteration that occurred during and after eruption.

Macaulayite was found by the late I. Stephen (Soil Science Department, University of Aberdeen) in an outcrop of reddened, deeply weathered granite, near Inverurie, Aberdeenshire. It is blood red in colour, very fine-grained, and has refractive indices greater than 1.734. Its calculated density is 4.41 g/cm3. The mean of fourteen electron microprobe analyses in the anhydrous form is Fe2O3 84.67, Al2O3 4.01, SiO2 11.32%. With thermogravimetric data this leads to a formula of (Al3.38)Si7.95O86(OH)4; the ideal formula is Si4O43(OH)2. The cell indexes as C-centred monoclinic with a 5.038, b 8.726, c 36.342Å, β 92°. The strongest X-ray lines are 36.6 (vs), 18.16 (vs), 3.700 (25), 2.720 (35), 2.533 (100), 2.214 (20), and 1.420 (35). Macaulayite has a layer structure, thought to consist of a double hematite unit terminated on both sides by silicate sheets and with water between these sheets. The infra-red spectrum includes absorption bands at 3597, 1052, 1033, and 858 cm−1, arising from the hydroxysilicate component of the mineral and at 647, 520, 438, 400, 304, and 227 cm−1 corresponding to the platy hematite unit. The mineral is named for the Macaulay Institute for Soil Research and the name was approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association prior to publication.

Electron-diffraction photographs of some natural and synthetic mullites and a typical sillimanite have been obtained and are interpreted using diffraction data due to Agrell and Smith. The position and diffuseness of mullite reflections (h0l) with l = ½ have been re-studied. In such reciprocal lattice sections maxima are symmetrically disposed in pairs about the positions of sillimanite reflections with l odd. They lie on a* rows and show different separations in the specimens studied. These diffraction conditions are closely analogous to those observed in the intermediate plagioclases (paired ‘e’ maxima) and in nepheline, and a similar explanation is envisaged in terms of antiphase domain structure. Intimate association of a mullite-type phase and sillimanite is shown to result from the breakdown of muscovite in a thermal metamorphic aureole, and a chemical analysis of a natural Fe,Ti-bearing mullite from a spinel-mullite buchite in the same aureole, is presented.

The occurrence of brookite aud anatase within the limits of the Dartmoor granite exposure was first indicated by a sample of stream-sand taken two years ago below the bridge at Dartmeet–a locality which is noteworthy for sands rich ill these and other accessory minerals of the Dartmoor granite.

Anatase, either alone or associated with brookite in small amounts, was found in a majority of the sands taken the following year at selected points along (1) the Plym River, between Cadover Bridge and Hatter Tor, (2) the East Dart and the West Dart, upstream from Dartmeet, (3) the West Webburn, upstream from Ponsworthy, (4) the East Webburn, upstream from Lizwell Meet, and (5) minor streams in the Hamel Down-Bonehill Down area. Rutile proved to be a rare mineral, liable to be overlooked in a residue containing brown cassiterite, from which it cannot readily be distinguished except by microchemical means.

Natural cobalt hydroxide is CoO.OH, not Co(OH)2 as has recently been asserted; for this mineral the name heterogenite has priority. Copper, frequently present, may be in solid solution as (Co,Cu)(O,OH)OH, or may be as finely divided malachite; for cuprian heterogenite, the name schulzenite has priority.