Steinmetzite, ideally Zn2Fe3+(PO4)(2)(OH)center dot 3H(2)O, is a new mineral from the Hagendorf-Stid pegmatite, Flagendorf, Oberpfalz, Bavaria, Gennany. Steinmetzite was found in a highly oxidized zone of the Cornelia mine at Hagendorf-Stid. It has formed by alteration of phosphophyllite, involving oxidation of the iron and some replacement of Zn by Fe. Steinmetzite lamellae co-exist with an amorphous Fe-rich phosphate in pseudomorphed phosphophyllite crystals. The lamellae are only a few um thick and with maximum dimension similar to 50 mu m. The phosphophyllite pseudomorphs have a milky opaque appearance, often with a glazed yellow to orange weathering rind and with lengths ranging from sub-mm to 1 cm. Associated minerals are albite, apatite, chalcophanite, jahnsite, mitridatite, muscovite, quartz and wilhelmgrimbelite. Goethite and cryptomelane are also abundant in the oxidized zone. The calculated density is 2.96 g cm(-3). Steinmetzite is biaxial (-) with measured refractive indices alpha = 1.642(2), beta = 1.659 (cal c.), gamma = 1.660(2) (white light). 2V(meas) = 27(1)degrees; orientation is Y approximate to b, X <^>c approximate to 27 degrees, with crystals flattened on {010} and elongated on [001]. Pleochroism shows shades of pale brown; Y > X approximate to Z. Electron microprobe analyses (average of seven crystals) with Fe reported as Fe2O3 and with H2O calculated from the structure gave ZnO 31.1, MnO 1.7, CaO 0.5, Fe2O3 21.9, Al2O3 0.3, P(2)o(5) 32.9, H2O 14.1 wt.%, total 102.5%. The empirical formula based on 2 P and 12 0, with all iron as ferric and OH adjusted for charge balance is Zn1.65Fe1.193+Mn0.112+ Ca0.03Al0.023+(PO4)(2)(OH)(1.21)center dot 2.79H(2)O. The simplified formula is Zn2Fe3+(PO4)(2)(OH)center dot 3H(2)O. Steinmetzite is triclinic, PI, with unit-cell parameters: a = 10.438(2), b= 5.102(1), c = 10.546(2) angstrom, alpha = 91.37(2), beta = 115.93(2) and gamma = 94.20(2)degrees. V= 502.7(3) angstrom(3), Z=2. The strangest lines in the powder X-ray diffraction pattern are [d(obs) in angstrom (I) (hkl)] 9.313(65) (100), 5.077(38) (010), 4.726(47) (002), 4.657(100) (200), 3.365 (55) ((3) over bar 02), 3.071(54) (1 (1) over bar2) and 2.735(48) ((3) over bar(1) over bar2). The structure is related to that of phosphophyllite.

A comparative study is presented of the chemistry and crystallography of zinc-bearing strunzites from Hagendorf Sud, 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 Sud 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 Sud 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 MFe32+(PO4)(2)(OH)(2)center dot 6 center dot 5H(2)O, 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, MFe32+(PO4)(2)(OH)(2)center dot 6 center dot 5H(2)O, which has no interlayer water. Interestingly, the zincostrunzites from the two localities differ in the location of the interlayerwatermolecule, with a corresponding difference in theHbonding.

Wilhelmgiimbelite, ideally [ZnFe2+Fe33+ (PO4)(3)(OH)(4)(H2O)(5)]center dot 2H(2)O, is a new secondary phosphate mineral related closely to schoonerite, [ZnMnFe2+Fe33+ (PO4)(3)(OH)(4)(H2O)(5)]center dot 2H(2)O, from oxidized zones of the Hagendorf-Siid pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Wilhelingtimbelite 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 10101. 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 wilhelmgfimbelite is 2.82 g cm(3). It is optically biaxial (+) with alpha =1.560(2), beta= 1.669(2), gamma =1.718(2), 2V(meas) = 63(1)degrees and 2V(calc.) = 65 degrees. Dispersion is weak with r > v, orientation X=b, Y=c, Z=a. Pleochroism is weak, with colours Z = orange brown, Y= yellow brown, X= light yellow brown, 7. >> Y> X. Electron microprobe analyses (average of seven analyses, seven crystals) with 1120 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. X). The empirical formula, scaled to 3 P and OH adjusted for charge balance is Zn1.50Mn0.272+Fe2.333+(PO4)(3)center dot(OH)(2.73)(H2O)(8.27). The structural formula is [Zn(Mn0.27Fe0.733+) El 0 (Zn0.25Fe0.152+Fe0.603+)(Sigma 1.0)(Zn0.25Fe0.452+)Sigma(0.7) Fe3+(PO4)(3),(OH,H2O)(9)vertical bar center dot 2H(2)O. Wilhelmgrimbelite has orthorhombic symmetry, Pmab, Z = 4, with the unit-cell parameters of a = 10.987(7) angstrom, b= 25.378(13) angstrom, c = 6.387(6) angstrom and 17= I 781(2) angstrom(3). The strongest lines in the powder X-ray diffiaction pattern are [d(obs) in angstrom(I-obs) (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). Wilhelmgumbelite 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. Wilhelmgiimbelite also differs structurally from schoonerite in having partial occupation of one of the Fe sites, which appears to be correlated with the Zn partitioning.

Kummerite, ideally Mn2+Fe3+Al(PO4)(2)(OH)(2).8H(2)O, is a new secondary phosphate mineral belonging to the laueite group, from the Hagendorf-Sdegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Kummerite occurs as sprays or rounded aggregates of very thin, typically deformed, amber yellow laths. Cleavage is good parallel to {010}. The mineral is associated closely with green Zn-and Al-bearing beraunite needles. Other associated minerals are jahnsite-(CaMnMn) and Al-bearing frondelite. The calculated density of kummerite is 2.34 g cm(-3). It is optically biaxial (-), alpha = 1.565(5), beta = 1.600(5) and gamma = 1.630(5), with weak dispersion. Pleochroism is weak, with amber yellow tones. Electron microprobe analyses (average of 13 grains) with H2O and FeO/Fe2O3 calculated on structural grounds and normalized to 100%, gave Fe2O3 17.2, FeO 4.8, MnO 5.4, MgO 2.2, ZnO 0.5, Al2O3 9.8, P2O5 27.6, H2O 32.5, total 100 wt.%. The empirical formula, based on 3 metal apfu is (Mn0.372+Mg0.27Zn0.03Fe0.333+)(Sigma 1.00)(Fe1.063+Al0.94)(Sigma 2.00)PO4)(1.91)(OH)(2.27)(H2O)(7.73). Kummerite is triclinic, P (1) over bar, with the unit-cell parameters of a = 5.316(1) angstrom, b = 10.620(3) angstrom, c = 7.118(1) angstrom, alpha = 107.33(3)degrees, beta = 111.22(3)degrees, gamma = 72.22(2)degrees and V = 348.4(2) angstrom(3). The strongest lines in the powder X-ray diffraction pattern are [d(obs) in angstrom(I) (hkl)] 9.885 (100) (010); 6.476 (20) (001); 4.942 (30) (020); 3.988 (9) ((1) over bar 10); 3.116 (18) ((1) over bar 20); 2.873 (11) ((1) over bar 21). Kummerite is isostructural with laueite, but differs in having Al and Fe3+ ordered into alternate octahedral sites in the 7.1 angstrom trans-connected octahedral chains.

Flurlite, ideally Zn3Mn(2+) Fe3+( PO4) 3( OH) 2 . 9H(2)O, is a new mineral from the Hagendorf- Sud pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Flurlite occurs as ultrathin (< 1 mu m) 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 (-), alpha = 1.60( 1), beta = 1.65( 1) and gamma = 1.68( 1), with weak dispersion and parallel extinction, X approximate to c, Y approximate to a, Z approximate to 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)angstrom, beta = 99.34 ( 3)degrees The strongest lines in the X- ray powder diffraction pattern are [ dobs in angstrom(I) (hkl)] 12.900( 100)( 001); 8.375( 10)( 011); 6.072( 14)( 1 _ 01); 5.567( 8)( 012); 4.297( 21)( 003); 2.763( 35)( 040). Flurlite ( R1 = 0.057 for 995 F > 4s( 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 x 11.1 angstrom. The different symmetry ( orthorhombic, Pmab) for schoonerite reflects a different topology of the layers.

Crystals of laueite, Mn2+ Fe-2(3+)(PO4)(2)(OH)(2).8H(2)O, from the Cornelia mine open cut, Hagendorf Sud, 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 angstrom corner-connected octahedral chains. The coordination polyhedra are different for the two sites, M2O(4)(OH)(2) and M3O(2)(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.

Whiteite-(CaMnMn), CaMnMn2Al2[PO4](4)(OH)(2)center dot 8H(2)O, is a new hydrous phosphate of Ca, Mn and Al, which is closely related to both jahnsite-(CaMnMn) and the minerals of the whiteite group. It is monoclinic, P2/a, with a = 15.02(2), b = 6.95(1), c = 10.13(3) angstrom, beta = 111.6(1)degrees, V = 983.3(6) angstrom(3), Z = 2 (from powder diffraction data) or a = 15.020(5), b = 6.959(2), c = 10.237(3) angstrom, beta = 111.740(4)degrees, V = 984.3(5) angstrom(3), Z = 2 (from single-crystal diffraction data). The mineral was found in the Hagendorf Sud granitic pegmatite (Germany) as small (up to 0.5 mm in size) crystals elongated on a and tabular on {010}. The crystals are either simply or polysynthetically twinned on {001}. They crystallize on the walls of voids within altered zwieselite crystals or form coronas (up to 1 mm in diameter) around cubic crystals of uraninite. The mineral is transparent, colourless to pale yellow (depending on Al-Fe3+ substitution), with a vitreous lustre and a white streak. The cleavage is perfect on {001}, the fracture is stepped and the Mohs hardness is 3 1/2. In transmitted light, the mineral is colourless; dispersion was not observed. Whiteite-(CaMnMn) is biaxial (+), alpha = 1.589(2), beta = 1.592(2), gamma = 1.601(2) (589 nm), 2V(meas) = 60(10)degrees, 2V(calc) = 60.3 degrees. The optical orientation is X = b, Z boolean AND a = 5 degrees. The calculated and measured densities are D-calc = 2.768 and D-meas = 2.70(3) g cm(-3), respectively. The mean chemical composition determined by electron microprobe is Na2O 0.53, MgO 0.88, Al2O3 11.66, P2O5 34.58, CaO 4.29, MnO 17.32, FeO 8.32, ZnO 2.60 wt.%, with H2O 19.50 wt.% (determined by the Penfield method), giving a total of 99.68 wt.%. The empirical formula calculated on the basis of four phosphorus atoms per formula unit, with ferric iron calculated to maintain charge balance, is (Ca0.63Zn0.26Na0.14)(Sigma 1.03) (Mn0.60Fe0.402+)(Sigma 1.00)(Mn1.40Fe0.372+Mg0.18Fe0.063+)(Sigma 2.01)(Al1.88Fe0.123+)(Sigma 2.00)[PO4](4)(OH)(2)center dot 7.89H(2)O. The simplified formula is CaMnMn2Al2[PO4](4)(OH)(2)center dot 8H(2)O. The mineral is easily soluble in 10% HCl at room temperature. The strongest X-ray powder-diffraction lines [listed as d in angstrom (I) (hkl)] are as follows: 9.443(65)(001), 5.596(25)(011), 4.929(80)(210), 4.719(47)(002), 3.494(46)(400), 2.7958(100)(022). The crystal structure of whiteite-(CaMnMn) was refined for a single crystal twinned on (001) to R-1 = 0.068 on the basis of 5702 unique observed reflections. It is similar to the structures of other members of the whiteite group. The mineral is named for the chemical composition, in accordance with whiteite-group nomenclature.

Whiteite-(CaMnMn), CaMnMn2Al2[PO4](4)(OH)(2)center dot 8H(2)O, is a new hydrous phosphate of Ca, Mn and Al, which is closely related to both jahnsite-(CaMnMn) and the minerals of the whiteite group. It is monoclinic, P2/a, with a = 15.02(2), b = 6.95(1), c = 10.13(3) angstrom, beta = 111.6(1)degrees, V = 983.3(6) angstrom(3), Z = 2 (from powder diffraction data) or a = 15.020(5), b = 6.959(2), c = 10.237(3) angstrom, beta = 111.740(4)degrees, V = 984.3(5) angstrom(3), Z = 2 (from single-crystal diffraction data). The mineral was found in the Hagendorf Sud granitic pegmatite (Germany) as small (up to 0.5 mm in size) crystals elongated on a and tabular on {010}. The crystals are either simply or polysynthetically twinned on {001}. They crystallize on the walls of voids within altered zwieselite crystals or form coronas (up to 1 mm in diameter) around cubic crystals of uraninite. The mineral is transparent, colourless to pale yellow (depending on Al-Fe3+ substitution), with a vitreous lustre and a white streak. The cleavage is perfect on {001}, the fracture is stepped and the Mohs hardness is 3 1/2. In transmitted light, the mineral is colourless; dispersion was not observed. Whiteite-(CaMnMn) is biaxial (+), alpha = 1.589(2), beta = 1.592(2), gamma = 1.601(2) (589 nm), 2V(meas) = 60(10)degrees, 2V(calc) = 60.3 degrees. The optical orientation is X = b, Z boolean AND a = 5 degrees. The calculated and measured densities are D-calc = 2.768 and D-meas = 2.70(3) g cm(-3), respectively. The mean chemical composition determined by electron microprobe is Na2O 0.53, MgO 0.88, Al2O3 11.66, P2O5 34.58, CaO 4.29, MnO 17.32, FeO 8.32, ZnO 2.60 wt.%, with H2O 19.50 wt.% (determined by the Penfield method), giving a total of 99.68 wt.%. The empirical formula calculated on the basis of four phosphorus atoms per formula unit, with ferric iron calculated to maintain charge balance, is (Ca0.63Zn0.26Na0.14)(Sigma 1.03) (Mn0.60Fe0.402+)(Sigma 1.00)(Mn1.40Fe0.372+Mg0.18Fe0.063+)(Sigma 2.01)(Al1.88Fe0.123+)(Sigma 2.00)[PO4](4)(OH)(2)center dot 7.89H(2)O. The simplified formula is CaMnMn2Al2[PO4](4)(OH)(2)center dot 8H(2)O. The mineral is easily soluble in 10% HCl at room temperature. The strongest X-ray powder-diffraction lines [listed as d in angstrom (I) (hkl)] are as follows: 9.443(65)(001), 5.596(25)(011), 4.929(80)(210), 4.719(47)(002), 3.494(46)(400), 2.7958(100)(022). The crystal structure of whiteite-(CaMnMn) was refined for a single crystal twinned on (001) to R-1 = 0.068 on the basis of 5702 unique observed reflections. It is similar to the structures of other members of the whiteite group. The mineral is named for the chemical composition, in accordance with whiteite-group nomenclature.

Abstract 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 P1̄ 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.

Nordgauite, MnAl2(PO4)(2)(F,OH)(2)center dot 5H(2)O, is a new secondary phosphate from the Hagendorf-Sud 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 pm long and 10 pm 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. D-meas. and D-calc. 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, Al2O3 22.84, P2O5 31.62, F 5.13 and H2O 22.86 (by CHN), less F=O 2.16, total 96.50. The corresponding empirical formula is (Mn0.90Ca0.08Fe0.04Zn0.01Mg0.01)-(Sigma 1.04Al2.01)(PO4)(2)[F-1.21,(OH)(0.90)](Sigma 2.11)center dot 5.25H(2)O. Nordgauite is triclinic, space group P (1) over bar, with the unit-cell parameters: a = 9.920(4), b = 9.933(3), c = 6.087(2) angstrom, alpha = 92.19(3), beta = 100.04(3), gamma = 97.61(3)degrees, V = 584.2(9) angstrom(3) and Z = 2. The strongest lines in the XRD powder pattern are [d in angstrom (I) (hkI)] 9.806 (100)(010). 7.432 (40)(1 $(1) over bar $0), 4.119 (20)(210), 2.951 (16)(0 $(3) over bar $1), 4.596 (12)(2 $(1) over bar $0), 3.225 (12)(220) and 3.215 (12)(121). The structure of nordgauite was solved using synchrotron XRD data collected on a 60 mu m x 3 mu m x 4 mu m needle and refined to R-1 = 0.0427 for 2374 observed reflections with F > 4 sigma(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.

Meurigite is a new hydrated potassium iron phosphate related to kidwellite and with structural similarities to other late-stage fibrous ferric phosphate species. It has been found at four localities so far - the Santa Rita mine, New Mexico, U.S.A.; the Hagendorf-Sud pegmatite in Bavaria, Germany; granite pegmatite veins at Wycheproof, Victoria, Australia; and at the Gold Quarry Mine, Nevada, U.S.A. The Santa Rita mine is the designated type locality. Meurigite occurs as tabular, elongated crystals forming spherical and hemispherical clusters and drusy coatings. The colour ranges from creamy white to pale yellow and yellowish brown. At the type locality, the hemispheres may reach 2 mm across, but the maximum diameter reached in the other occurrences is usually less than 0.5 mm. A wide variety of secondary phosphate minerals accompanies meurigite at each locality, with dufrenite, cyrilovite, beraunite, rockbridgeite and leucophosphite amongst the most common. Vanadates and uranates occur with meurigite at the Gold Quarry mine. Electron microprobe analysis and separate determination of H2O and CO2 on meurigite from the type locality gave a composition for which several empirical formulae could be calculated. The preferred formula, obtained on the basis of 35 oxygen atoms, is (K0.85Na0.03)(Sigma 0.88)(Fe7.013+Al0.16Cu0.02)(Sigma 7.19) (PO4)(5.11)(CO3)(0.20)(OH)(6.7). 7.25H(2)O, which simplifies to KFe73+(PO4)(5)(OH)(7) . 8H(2)O. Qualitative analyses only were obtained for meurigite from the other localities, due to the softness and openness of the aggregates. Because of the fibrous nature of meurigite, it was not possible to determine the crystal structure, hence the exact stoichiometry remains uncertain. The lustre of meurigite varies from vitreous to waxy for the Santa Rita mine mineral, to silky for the more open sprays and internal surfaces elsewhere. The streak is very pale yellow to cream and the estimated Mohs hardness is about 3. Cleavage is perfect on {001} and fragments from the type material have a mean specific gravity of 2.96. The strongest lines in the X-ray powder pattern for the type material are (d(obs),I-obs,hkl) 3.216(100)404; 4.84(90)111; 3.116(80)205; 4.32(70)112; 9.41(60)201; 3.470(60)800. The X-ray data were indexed on the basis of a monoclinic unit cell determined from electron diffraction patterns. The cell parameters, refined by least squares methods, are a = 29.52(4), b = 5.249(6), c = 18.26(1) Angstrom, beta = 109.27(7)degrees, V = 2672(3) Angstrom(3), and Z = 4. The calculated density is 2.89 gcm(-3). The space group is either C2, Cm or C2/m. X-ray powder data for meurigite are closely similar to those for kidwellite and phosphofibrite, but meurigite appears to be characterised by a strong 14 Angstrom reflection. The relationship between these three minerals remains uncertain in the absence of structural data. On the available evidence, meurigite and kidwellite are not the respective K and Na-endmembers of a solid solution series. The meurigite cell parameters suggest it belongs to a structural family of fibrous ferric phosphates, such as rockbridgeite, dufrenite and beraunite, which have a discrete 5 Angstrom fibre axis. Meurigite occurs in widely varying environments, its formation probably favoured by late-stage solutions rich in K rather than Na.