Aldermanite from Tom's quarry in the Kapunda–Angaston area of the Mount Lofty Ranges, South Australia has been characterised by electron microprobe analyses and single-crystal structure analysis. The empirical formula is Na0.72K0.13Ca0.06Mg1.15Al2.92(PO4)2.05[(OH)2.92F2.96]Σ5.88⋅8.91H2O, based on 23 anions. Analysis of a specimen from the type locality, the nearby Klemm's quarry, Moculta, gave a similar formula, Na0.59K0.06Ca0.36Mg0.92Al3.16(PO4)1.97[(OH)4.08F2.70]Σ6.78⋅8.36H2O. Na and F were not analysed in the original description of the mineral. The ideal end-member formula is [Mg(H2O)6][Na(H2O)2Al3(PO4)2(OH)6]⋅H2O, compared to the original formula of Mg5Al12(PO4)8(OH)22⋅nH2O with n ≈ 32. Aldermanite is monoclinic, P21/c with a = 13.524(3), b = 9.958(2), c = 7.013(1) Å and β = 97.40(3)°. The crystal structure of aldermanite is built from sawtooth layers of cis- and trans-corner-connected, Al-centred octahedra, decorated with corner-connected PO4 tetrahedra to give (100) layers of composition Al3(PO4)2(OH,F)6. Interlayer Mg(H2O)6 octahedra and H2O molecules hold the layers together through H bonding. The corner-connected octahedra form 6-membered rings that are centred by 8-coordinated Na and have a topology identical to a 3-octahedra-wide {110} slice of the pyrochlore structure. This pyrochlore element contains intersecting kagomé nets of Al atoms, parallel to (111) and (11$\bar{1}$) of cubic pyrochlore. Minerals of the walentaite group, as well as zirconolite-3O polytypes have the same type of intersecting kagomé nets of small cations.

During the last fifteen years there has been a paradigm shift in the continuum modelling of granular materials; most notably with the development of rheological models, such as the $\mu (I)$-rheology (where $\mu$ is the friction and I is the inertial number), but also with significant advances in theories for particle segregation. This paper details theoretical and numerical frameworks (based on OpenFOAM) which unify these currently disconnected endeavours. Coupling the segregation with the flow, and vice versa, is not only vital for a complete theory of granular materials, but is also beneficial for developing numerical methods to handle evolving free surfaces. This general approach is based on the partially regularized incompressible $\mu (I)$-rheology, which is coupled to the gravity-driven segregation theory of Gray & Ancey (J. Fluid Mech., vol. 678, 2011, pp. 353–588). These advection–diffusion–segregation equations describe the evolving concentrations of the constituents, which then couple back to the variable viscosity in the incompressible Navier–Stokes equations. A novel feature of this approach is that any number of differently sized phases may be included, which may have disparate frictional properties. Further inclusion of an excess air phase, which segregates away from the granular material, then allows the complex evolution of the free surface to be captured simultaneously. Three primary coupling mechanisms are identified: (i) advection of the particle concentrations by the bulk velocity, (ii) feedback of the particle-size and/or frictional properties on the bulk flow field and (iii) influence of the shear rate, pressure, gravity, particle size and particle-size ratio on the locally evolving segregation and diffusion rates. The numerical method is extensively tested in one-way coupled computations, before the fully coupled model is compared with the discrete element method simulations of Tripathi & Khakhar (Phys. Fluids, vol. 23, 2011, 113302) and used to compute the petal-like segregation pattern that spontaneously develops in a square rotating drum.

The SPARC tokamak is a critical next step towards commercial fusion energy. SPARC is designed as a high-field ($B_0 = 12.2$ T), compact ($R_0 = 1.85$ m, $a = 0.57$ m), superconducting, D-T tokamak with the goal of producing fusion gain $Q>2$ from a magnetically confined fusion plasma for the first time. Currently under design, SPARC will continue the high-field path of the Alcator series of tokamaks, utilizing new magnets based on rare earth barium copper oxide high-temperature superconductors to achieve high performance in a compact device. The goal of $Q>2$ is achievable with conservative physics assumptions ($H_{98,y2} = 0.7$) and, with the nominal assumption of $H_{98,y2} = 1$, SPARC is projected to attain $Q \approx 11$ and $P_{\textrm {fusion}} \approx 140$ MW. SPARC will therefore constitute a unique platform for burning plasma physics research with high density ($\langle n_{e} \rangle \approx 3 \times 10^{20}\ \textrm {m}^{-3}$), high temperature ($\langle T_e \rangle \approx 7$ keV) and high power density ($P_{\textrm {fusion}}/V_{\textrm {plasma}} \approx 7\ \textrm {MW}\,\textrm {m}^{-3}$) relevant to fusion power plants. SPARC's place in the path to commercial fusion energy, its parameters and the current status of SPARC design work are presented. This work also describes the basis for global performance projections and summarizes some of the physics analysis that is presented in greater detail in the companion articles of this collection.

Non-stoichiometric, carbon-containing crandallite from Guatemala and plumbogummite from Cumbria have been characterized using electron microprobe (EMPA) and wet-chemical analyses, Rietveld analysis of powder X-ray diffraction (PXRD) patterns, and infrared (IR), Raman and cathodoluminescence (CL) spectroscopies. The samples contain 11.0 and 4.8 wt.% CO2, respectively. The IR spectra for both samples show a doublet in the range 1410–1470 cm–1, corresponding to CO3 vibrations. Direct confirmation of CO3 replacing PO4 was obtained from difference Fourier maps in the Rietveld analysis. Carbonate accounts for 67% of the C in the plumbogummite and 20% of the C in the Guatemalan crandallite, the remainder being present as nano-scale organic carbon. The CO3 substitution for PO4 is manifested in a large contraction of the tetrahedral volume (14–19%) and by a contraction of the a axis, analogous to observations for carbonate-containing fluorapatites. Stoichiometric crandallite from Utah was characterized using the same methods, for comparison with the non-stoichiometric, carbon-bearing phases.

The type specimen of liskeardite, (Al, Fe)3AsO4(OH)6·5H2O, from the Marke Valley Mine, Liskeard District, Cornwall, has been reinvestigated. The revised composition from electron microprobe analyses and structure refinement is [Al29.2Fe2.8(AsO4)18(OH)42(H2O)22]·52H2O. The crystal structure was determined using synchrotron data collected on a 2 μm diameter fibre at 100 K. Liskeardite has monoclinic symmetry, space group I2, with the unit-cell parameters a = 24.576(5), b = 7.754(2) Å, c = 24.641(5) Å, and β = 90.19(1)º. The structure was refined to R = 0.059 for 9769 reflections with I > 3σ(I). It is of an open framework type in which intersecting polyhedral slabs parallel to (101) and (10) form 17.4 Å × 17.4 Å channels along [010], with water molecules occupying the channels. Small amounts (<1 wt.%) of Na, K and Cu are probably adsorbed at the channel walls The framework comprises columns of pharmacoalumite-type, intergrown with chiral chains of six cis edge-shared octahedra. It can be described in terms of cubic close packing, with vacancies at both the anion and cation sites. The compositional and structural relationships between liskeardite and pharmacoalumite are discussed and a possible mechanism for liskeardite formation is presented.

Nordgauite, MnAl2(PO4)2(F,OH)2·5H2O, is a new secondary phosphate from the Hagendorf-Süd pegmatite, Bavaria, Germany. It occurs as white to off-white compact waxy nodules and soft fibrous aggregates a few millimetres across in altered zwieselite—triplite. Individual crystals are tabular prismatic, up to 200 μ long and 10 μ wide. Associated minerals include fluorapatite, sphalerite, uraninite, a columbite—tantalite phase, metastrengite, several unnamed members of the whiteite—jahnsite family, and a new analogue of kingsmountite. The fine-grained nature of nordgauite meant that only limited physical and optical properties could be obtained; streak is white; fracture, cleavage and twinning cannot be discerned. Dmeas. and Dcaic. are 2.35 and 2.46 g cm–3, respectively; the average RI is n = 1.57; the Gladstone-Dale compatibility is —0.050 (good). Electron microprobe analysis gives (wt.%): CaO 0.96. MgO 0.12, MnO 14.29, FeO 0.60, ZnO 0.24, A12O3 22.84, P2O5 31.62, F 5.13 and H2O 22.86 (by CHNX less F=O 2.16, total 96.50. The corresponding empirical formula is (Mn0.90Ca0.08Fe0.04Zn0.01Mg0.01)-Σi.04Ai2.0i(PO4)2[F1.21,(OH)0.90]Σ2.11·5.25H2O. Nordgauite is triclinic, space group P1̄, with the unit-cell parameters: a = 9.920(4), b = 9.933(3), c = 6.087(2) Å, α = 92.19(3), β = 100.04(3), γ = 97.61(3)°, V = 584.2(9) Å3 and Z = 2. The strongest lines in the XRD powder pattern are [d in Å (I) (hkl)] 9.806 (100)(010), 7.432 (40)(l1̄0), 4.119 (20)(210), 2.951 (16)(031), 4.596 (12)(21̄O), 3.225 (12)(220) and 3.215 (12)(121). The structure of nordgauite was solved using synchrotron XRD data collected on a 60 μm × 3 μm × 4 μm needle and refined to R1 = 0.0427 for 2374 observed reflections with F > 4σ(F). Although nordgauite shows stoichiometric similarities to mangangordonite and kastningite, its structure is more closely related to those of vauxite and montgomeryite in containing zig-zag strings of corner-connected Al-centred octahedra along [011], where the shared corners are alternately in cis and trans configuration. These chains link through corner-sharing with PO4 tetrahedra along [001] to form (100) slabs that are interconnected via edge-shared dimers of MnO6 polyhedra and other PO4 tetrahedra.

Kleberite, ideally Fe3+Ti6O11(OH)5, is a new mineral (IMA 2012-023) from Tertiary sands at Königshain, Saxony, northeast Germany. It is also found in heavy mineral sands from the Murray Basin, southeast Australia and at Kalimantan, Indonesia. It occurs as rounded anhedral to euhedral translucent grains, 0.04 0.3 mm across, which are generally red-brown, but grade to orange with decreasing iron content. Associated minerals include ilmenite, pseudorutile, 'leucoxene', tourmaline and spinel. The density measured by pycnometry is 3.28 g cm-3, which is lower than the calculated density of 3.91 g cm-3, due to intragrain porosity which is not penetrated by the immersion fluid. The intragrain pores, of median diameter 18 nm, are partially filled with impurity phases including kaolinite, diaspore and quartz. Kleberite grains have a uniaxial (–) character, but localized regions are weakly biaxial (–) with 2V close to zero. The mean refractive index, calculated from reflectance measurements, is 2.16(3). The mean empirical formula from electron-microprobe analyses of 15 Königshain kleberite grains is Fe3+1.01Mg0.06Ti6O11.2(OH)4.8[Al0.59Si0.31P0.04O1.60·1.8H2O], where the formula element in square brackets represents impurities in the pores. Kleberite forms over a compositional range with [Ti]/[Fe + Ti] atomic ratios from 0.8–0.9. It has monoclinic symmetry, P21/c, with a = 7.537(1), b = 4.5795(4), c = 9.885(1) Å , β = 131.02(1)°. The six strongest lines in the powder X-ray diffraction (XRD) pattern [listed as d in Å (I)] are as follows: 1.676(100), 2.170(82), 2.466(27), 1.423(22), 3.933(8), 2.764(9). The structure was refined by the Rietveld method on powder XRD data to Rp = 6.3, Rwp = 8.1, RB = 4.0. Kleberite is isostructural with tivanite; their structural formulae are [Ti4+3□][Ti4+3Fe3+]O11 (OH)5 and [Ti4+4][V3+4]O12(OH)4, respectively. Kleberite has dominant Ti4+ in place of V3+ in the M(2) metal-atom site. The related mineral pseudorutile, [Ti4][(Fe3+,Ti)4](O,OH)16, with Fe3+ > Ti4+ has dominant Fe3+ in this site. Kleberite grains from different localities commonly contain residual MgO-rich ferrian ilmenite. The chemical and physical relationships between the ilmenite and coexisting kleberite are used to evaluate different alteration mechanisms involving selective leaching of divalent oxides from ilmenite and pseudomorphic replacement reactions, respectively.

X-ray spectromicroscopy has been applied to the characterization of weathered ilmenite sand samples from Australian localities. X-ray absorption near edge spectroscopy (Xanes) studies were performed at the K-edges of the major elements Fe and Ti and minor impurity elements Mn and Cr. An extended suite of reference samples with crystallite sizes ranging from 1 nm to μm size were measured to establish if the absorption edge characteristics were influenced by crystal size effects. No changes were detected for oxides of Cr3+, Fe3+ or Ti4+, but the mixed Fe2+/Fe3+ oxide, Fe3O4, showed an edge shift to higher energies (by 1.5 eV) in a nanocrystalline sample. The Xanes study of a composite ilmenite grain with an unweathered primary ilmenite core and a highly weathered rim showed that Fe was present as Fe2+ in the core and Fe3+ in the rim whereas Mn was present as Mn2+ in both core and rim. Chromium, which is incorporated into the grains during weathering, is present predominantly as Cr3+, although minor (~15%) Cr6+ also occurs in highly weathered grains. The absorption K-edges of Fe3+ and Mn2+ are shifted markedly (by 2–3 eV) to higher energies in titanate phases relative to the binary oxides Fe2O3 and MnO.

Ilmenite concentrates obtained from heavy mineral deposits in the Murray Basin, southeastern Australia contain appreciable quantities (up to 10 wt.%) of an unusual hydrated Fe titanate mineral in the form of orange to red coloured translucent grains. The grains are weakly magnetic and have a low apparent density (<3.3 g cm–3) due to microprosity, which enables them to be easily concentrated in a pure state. Samples from different deposits have similar analyses of 67–69% TiO2, 8 –9% Fe2O3, 2–3% FeO, 11 –12% H2O and 8 –9% of intra-pore impurities, mainly SiO2 and Al2O3. The powder pattern for the mineral closely matches that for pseudorutile; having a hexagonal subcell with a = 2.844 (1) Å, c = 4.575 (1) Å. The idealized composition range of the Fe titanate, calculated from analyses and structure refinements, is [FeTi6O12(OH)3].3H2O to [FeTi6O11(OH)5].2H2O. The molecular water is nonstructural, probably adsorbed on the surfaces of nano-scale domains of the mineral. Electron microprobe and scanning electron microscopy studies provide evidence for formation of the mineral by replacement reactions acting on MgO-rich ferrian ilmenite grains. The mineral represents a distinct intermediate in the chemical weathering of ilmenite, having a pseudorutile-like structure but a leucoxene-like composition. It is unusual in not having undergone any recrystallization to phases such as rutile and anatase.

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.

Bariopharmacoalumite-Q2a2b2c, Ba0.5(Cu,ZnO)0.1H0.6[Al4(OH)4(As0.9Al0.1O4)3]·5.5H2O, from the south mine of the old copper mine at Cap Garonne, France, has a 2 × 2 × 2 I-centred tetragonal superstructure of the basic pharmacosiderite-type structure. Cell parameters are a = 15.405(2) Å and c = 15.553(3) Å. The structure was determined and refined in I2m to R1= 0.057 for 2697 reflections with I > 2σ(I), using synchrotron X-ray data on a twinned crystal. The origin of the superlattice cell doubling was determined to be due predominantly to the ordering of Ba atoms in half of the [0 0 1] channels, centred at (0, 0, 0) and (½, ½, 0). The other channels, centred at (½, 0, 0) and (0, ½, 0), were found to be occupied by corner-connected chains of Cu/Zn-centred square planar units.

Secondary phosphate assemblages from the Hagendorf Süd granitic pegmatite, containing the new Mn-Al phosphate mineral, nordgauite, have been characterized using scanning electron microscopy and electron microprobe analysis. Nordgauite nodules enclose crystals of the jahnsite—whiteite group of minerals, showing pronounced compositional zoning, spanning the full range of Fe/Al ratios between jahnsite and whiteite. The whiteite-rich members are F-bearing, whereas the jahnsite-rich members contain no F. Associated minerals include sphalerite, apatite, parascholzite, zwieselite-triplite solid solutions and a kingsmountite-related mineral. The average compositions of whiteite and jahnsite from different zoned regions correspond to jahnsite-(CaMnMn), whiteite-(CaMnMn) and the previously undescribed whiteite-(CaMnFe) end-members. Mo-Kα CCD intensity data were collected on a twinned crystal of the (CaMnMn)-dominant whiteite and refined in P2/a to wRobs = 0.064 for 1015 observed reflections.

Lead-bearing phyllotungstite from the Clara mine in the central Black Forest, Germany has a formula (Cs0.41)Na0.14K0.05Pb2+2.01Ca0.26[W6+10.87Fe3+3.13O35.75(OH)6.25](O(H2O)3). X-ray diffraction patterns exhibit pseudohexagonal symmetry, but refinement of single-crystal synchrotron data has shown that the true symmetry is orthorhombic, Cmcm, with a = 7.298(1), b = 12.640(2), c = 19.582(4) Å, and that the pseudohexagonal character is due to submicrometre-scale cyclical twinning by rotation about the pseudohexagonal c axis. The structure can be described in terms of an ordered intergrowth, parallel to (001), of (111)py blocks with pyrochlore-type structures, which are ~6 Å in width, and two-layer wide regions with a hexagonal tungsten bronze (HTB) type structure. Caesium atoms occupy 18-coordinate cavities in the HTB regions, and H2O molecules occupy Φ sites in the A2B2O6Φ pyrochlore blocks. The lowering of symmetry from hexagonal to orthorhombic is due to partial ordering of W and Fe in the octahedral B sites and of Pb and vacancies in the A sites of the pyrochlore blocks. The ideal formula for the intergrowth structure (with no vacancies) is C 2A10[B14(O,OH)42]Φ4, where C is the cavity site in the HTB slabs. The mineral has only 21% occupancy of the C site and 25% occupancy of the A site, but full occupancy of the Φ site. There may be some mixing of Cs and H2O between the C and Φ sites.

Giant electromagnetic pulses (EMP) generated during the interaction of high-power lasers with solid targets can seriously degrade electrical measurements and equipment. EMP emission is caused by the acceleration of hot electrons inside the target, which produce radiation across a wide band from DC to terahertz frequencies. Improved understanding and control of EMP is vital as we enter a new era of high repetition rate, high intensity lasers (e.g. the Extreme Light Infrastructure). We present recent data from the VULCAN laser facility that demonstrates how EMP can be readily and effectively reduced. Characterization of the EMP was achieved using B-dot and D-dot probes that took measurements for a range of different target and laser parameters. We demonstrate that target stalk geometry, material composition, geodesic path length and foil surface area can all play a significant role in the reduction of EMP. A combination of electromagnetic wave and 3D particle-in-cell simulations is used to inform our conclusions about the effects of stalk geometry on EMP, providing an opportunity for comparison with existing charge separation models.

Flurlite, ideally Zn3Mn2+Fe3+(PO4)3(OH)2·9H2O, is a new mineral from the Hagendorf-Süd pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Flurlite occurs as ultrathin (<1 μm) translucent platelets that form characteristic twisted accordion-like aggregates. The colour varies from bright orange red to dark maroon red. Cleavage is perfect parallel to (001). The mineral occurs on mitridatite and is closely associated with plimerite. Other associated minerals are beraunite, schoonerite, parascholzite, robertsite and altered phosphophyllite. The calculated density of flurlite is 2.84 g cm–3. It is optically biaxial (–), α = 1.60(1), β= 1.65(1) and γ = 1.68(1), with weak dispersion and parallel extinction, X ≈ c, Y ≈ a, Z ≈ b. Pleochroism is weak, with colours: X = pale yellow, Y = pale orange, Z = orange brown. Electron microprobe analyses (average of seven) with FeO and Fe2O3 apportioned and H2O calculated on structural grounds, gave ZnO 25.4, MnO 5.28, MgO 0.52, FeO 7.40, Fe2O3 10.3, P2O5 27.2, H2O 23.1, total 99.2 wt.%. The empirical formula, based on 3 P a.p.f.u. is Zn2.5Mn2+0.6Fe2+0.8Mg0.1Fe3+(PO4)3(OH)2·9H2O. Flurlite is monoclinic, P21/m, with the unit-cell parameters (at 100 K) of a = 6.3710(13), b = 11.020(2), c = 13.016(3) Å, β = 99.34 (3)°. The strongest lines in the X-ray powder diffraction pattern are [dobs in Å(I) (hkl)] 12.900(100)(001); 8.375(10)(011); 6.072(14)(101); 5.567(8)(012); 4.297(21)(003); 2.763(35)(040). Flurlite (R1 = 0.057 for 995 F > 4σ(F)) has a heteropolyhedral layer structure, with layers parallel to (001) and with water molecules packing between the layers. The slab-like layers contain two types of polyhedral chains running parallel to [100]: (a) chains of edge-sharing octahedra containing predominantly Zn and (b) chains in which Fe3+-centred octahedra share their apices with dimers comprising Zn-centred trigonal bipyramids sharing an edge with PO4 tetrahedra. The two types of chains are interconnected by corner-sharing along [010]. A second type of PO4 tetrahedron connects the chains to MnO2(H2O)4 octahedra along [010] to complete the structure of the (001) slabs. Flurlite has the same stoichiometry as schoonerite, but with dominant Zn rather than Fe2+ in the edge-shared chains. Schoonerite has a similar heteropolyhedral layer structure with the same layer dimensions 6.4 × 11.1 Å. The different symmetry (orthorhombic, Pmab) for schoonerite reflects a different topology of the layers.

Crystals of laueite, Mn2+Fe23+(PO4)2(OH)2·8H2O, from the Cornelia mine open cut, Hagendorf Süd, Bavaria, are zoned due to aluminium incorporation at the iron sites, with analysed Al2O3 contents varying up to 11 wt.%. Synchrotron X-ray data were collected on two crystals with different Al contents and the structures refined. The laueite structure contains two independent Fe3+-containing sites; M2 and M3, which alternate in 7 Å corner-connected octahedral chains. The coordination polyhedra are different for the two sites, M2O4(OH)2 and M3O2(OH)2(H2O)2 respectively. The structure refinements show that Al preferentially orders into site M3. Refined site occupancies for M2 and M3 for the two crystals are: for crystal L-1, M2 = 0.70(1) Fe + 0.30(1) Al, M3 = 0.54(1) Fe + 0.46(1) Al and for crystal L-2, M2 = 0.67(1) Fe + 0.33(1) Al, M3 = 0.48(1) Fe + 0.52(1) Al. For crystal L-2, the octahedral chains have dominant Fe in M2, alternating with dominant Al in M3 along the chain, an ordering phenomenon not previously reported for laueite-related minerals.

A comparative study is presented of the chemistry and crystallography of zinc-bearing strunzites from Hagendorf Süd, Bavaria, Germany and the Sitio do Castelo mine, Folgosinho, Portugal. Electron microprobe analyses of samples from the two localities show quite different cation substitutions. The Hagendorf Süd mineral is a Zn-bearing ferristrunzite, with compositional zoning due to Zn2+ replacing predominantly Fe3+ as well as minor Mn2+, whereas the Portugese mineral is a Zn-bearing strunzite, in which Zn2+ replaces Mn2+, with minor replacement of Fe3+ by Mn3+. Zincostrunzite, with dominant Zn in the interlayer octahedrally coordinated site, is a new strunzite-group mineral that has been characterized at both locations. Analysis of single-crystal synchrotron data for zinc-bearing ferristrunzite and zincostrunzite crystals from Hagendorf Süd show that the structures of both minerals contain zeolitic water in the interlayer region. The formula for strunzite-group minerals containing the zeolitic water is MFe23+(PO4)2(OH)2·6.5H2O, M=Fe, Mn, Zn. This formulation agrees with that found for zincostrunzite from the Sitio do Castelo mine, but differs from that reported previously for strunzite, MFe2+(PO4)2(OH)2·6H2O, which has no interlayer water. Interestingly, the zincostrunzites from the two localities differ in the location of the interlayer water molecule, with a corresponding difference in the H bonding.

Wilhelmgümbelite, ideally [ZnFe2+Fe33+(PO4)3(OH)4(H2O)5]·2H2O, is a new secondary phosphate mineral related closely to schoonerite, [ZnMnFe22+Fe3+(PO4)3(OH)2(H2O)7]·2H2O, from oxidized zones of the Hagendorf-Süd pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Wilhelmgümbelite occurs as radiating sprays of needle-like rectangular laths, up to 0.2 mm long and with colour varying from light yellow brown to orange red. Cleavage is perfect parallel to {010}. The mineral is associated closely with an oxidized pseudomorph of phosphophyllite, recently named steinmetzite. Other associated minerals are albite, apatite, chalcophanite, jahnsite, mitridatite, muscovite and quartz. The calculated density of wilhelmgümbelite is 2.82 g cm–3. It is optically biaxial (+) with α = 1.560(2), β = 1.669(2), γ = 1.718(2), 2V(meas) = 63(1)° and 2V(calc.) = 65°. Dispersion is weak with r > v, orientation X = b, Y = c, Z = a. Pleochroism is weak, with coloursZ = orange brown, Y = yellow brown, X = light yellow brown, Z >> Y > X. Electron microprobe analyses (average of seven analyses, seven crystals) with H2O and FeO/Fe2O3 calculated on structural grounds, gave FeO 5.8, Fe2O3 25.0, MnO 2.6, ZnO 16.4, P2O5 28.7, H2O 23.4, total 101.9 wt.%. The empirical formula, scaled to 3 P and OH– adjusted for charge balance is Zn1.50Mn0.272+Fe0.602+Fe2.333+(PO4)3·(OH)2.73(H2O)8.27. The structural formula is [Zn(Mn0.27Fe0.733+)∑1.0(Zn0.25Fe0.152+Fe0.603+)∑1.0(Zn0.25Fe0.452+)∑0.7Fe3+(PO4)3(OH,H2O)9]·2H2O.Wilhelmgümbelite has orthorhombic symmetry, Pmab, Z = 4, with the unit-cell parameters of a = 10.987(7) Å, b = 25.378(13) Å, c = 6.387(6) Å and V = 1781(2) Å3. The strongest lines in the powder X-ray diffraction pattern are [dobs in Å(Iobs) (hkl)] 12.65 (100) (020); 8.339 (5) (120); 6.421 (14) (001); 6.228 (8) (011); 4.223 (30) (120) and 2.111 (7) (0 12 0). Wilhelmgümbelite is an oxidized form of schoonerite, with the Mn2+ replaced principally by Fe3+. Its structure differs from that of schoonerite in having the Zn partitioned between two different sites, one five-coordinated as in schoonerite and the other tetrahedrally coordinated. Wilhelmgümbelite also differs structurally from schoonerite in having partial occupation of one of the Fe sites, which appears to be correlated with the Zn partitioning.