ALBERT

Description: The new mineral chlorkyuygenite, Ca 12 Al 14 O 32 [(H 2 O) 4 Cl 2 ] ( I $$\overline{4}$$ 3 d , a =12.0285(1)Å, V =1740.34(3)Å 3 ), was discovered as an accessory mineral in Ca-humite zones of calcareous skarn xenoliths in ignimbrites of the Upper Chegem Caldera, Northern Caucasus, Kabardino-Balkaria, Russia. Rounded grains and crystals with tris-tetrahedral form of chlorkyuygenite up to 50μm and aggregates up to 100–150μm in size are enclosed in chegemite, reinhardbraunsite and srebrodolskite. Chlorkyuygenite also forms rims on wadalite crystals. Chegemite–fluorchegemite, reinhardbraunsite–kumtyubeite, rondorfite, hydroxylellestadite, lakargiite, perovskite, kerimasite, elbrusite, ettringite-group minerals, hydrocalumite, bultfonteinite, and minerals of the katoite–grossular series are associated with chlorkyuygenite. Larnite, spurrite and galuskinite are noted as relics in Ca-humites. Chlorkyuygenite is colourless, occasionally with a greenish or yellowish tint, and the streak is white. The mineral is transparent with strong vitreous lustre, it is isotropic, n =1.672(1) (589 nm). The microhardness VHN load 50 g is 632(37) kg mm –2 , corresponding to 5–51/2 hardness according to the Mohs scale; the calculated density is 2.941 g cm –3 . The calculated Gladstone-Dale’s compatibility factor 1–(K p /K c )=–0.016 is superior. The holotype specimen of chlorkyuygenite from the chegemite zone is characterized by relatively constant composition corresponding to the crystal-chemical formula Ca 11.979 (Al 12.986 Fe 3+ 0.823 Si 0.179 Ti 4+ 0.033 ) 14.021 O 32 [(H 2 O) 3.767 Cl 2.234 ] 6 . In the Raman spectra of chlorkyuygenite the following characteristic main bands are distinguished: 202, 321, 511, 705, 776 and 881 cm –1 . A broad band with two maxima near 3400 and 3200 cm –1 is observed in the OH region and it is related to H 2 O in the structural cages of chlorkyuygenite. The molecular water is completely released from the mineral structure at about 550°C. Chlorkyuygenite crystallized initially as chlormayenite, which later was altered under influence of volcanic gases containing water vapour.

Description: Megawite is a perovskite-group mineral with an ideal formula CaSnO3 that was discovered in altered silicate-carbonate xenoliths in the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus, Russia. Megawite occurs in ignimbrite, where it forms by contact metamorphism at a temperature 〉800{degrees}C and low pressure. The name megawite honours the British crystallographer Helen Dick Megaw (1907-2002) who did pioneering research on perovskite-group minerals. Megawite is associated with spurrite, reinhardbraunsite, rondorfite, wadalite, srebrodolskite, lakargiite, perovskite, kerimasite, elbrusite-(Zr), periclase, hydroxylellestadite, hydrogrossular, ettringite-group minerals, afwillite, hydrocalumite and brucite. Megawite forms pale yellow or colourless crystals up to 15 {micro}m on edge with pseudo-cubic and pseudo-cuboctahedral habits. The calculated density and average refractive index are 5.06 g cm-3 and 1.89, respectively. Megawite is Zr-rich and usually crystallizes on lakargiite, CaZrO3. The main bands in the Raman spectrum of megawite are at: 159, 183, 262, 283, 355, 443, 474, 557 and 705 cm-1. The unit-cell parameters and space group of megawite, derived from electron back scattered diffraction, are: a = 5.555(3), b = 5.708(2), c = 7.939(5) A, V = 251.8(1) A3, Pbnm, Z = 4; they are based on an orthorhombic structural model for the synthetic perovskite CaSn0.6Zr0.4O3.

Description: Three samples of the skarn mineral rustumite Ca 10 (Si 2 O7)2(SiO4)(OH)2Cl2, space group C 2/ c , a 7.6, b 18.5, c 15.5 Å, β 104°, with variable OH, Cl, F content were investigated by electron microprobe, single-crystal X-ray structure refinements, and Raman spectroscopy. "Rust1_LCl" is a low chlorine rustumite Ca 10 (Si 2 O7)2(SiO 4 )(OH 1.88 F 0.12 )(Cl 1.28, OH 0.72 ) from skarns associated with the Rize batholith near Ikizedere, Turkey. "Rust2_F" is a F-bearing rustumite Ca 10 (Si 2 O 7 ) 2 (SiO 4 )(OH 1.13 F 0.87 ) (Cl 1 96 OH 0.04 ) from xenoliths in ignimbrites of the Upper Chegem Caldera, Northern Caucasus, Russia. "Rust3_LCl_F" represents a low-Cl, F-bearing rustumite Ca10(Si 2 O7) 2 [(SiO4)0. 8 7(H4O 4 )0.13](OH1.01F0.99) (Cl 1.00 OH 1.00 ) from altered merwinite skarns of the Birkhin massif, Baikal Lake area, Eastern Siberia, Russia. Rustumite from Birkhin massif is characterized by a significant hydrogarnet-like or fluorine substitution at the apices of the orthosilicate group, leading to specific atomic displacements. The crystal structures including hydrogen positions have been refined from single-crystal X-ray data to R1 = 0.0205 (Rust1_LCl), R1 = 0.0295 (Rust2_F), and R1 = 0.0243 (Rust3_LCl_F), respectively. Depletion in Cl and replacement by OH is associated with smaller unit-cell dimensions. The substitution of OH by F leads to shorter hydrogen bonds O-H···F instead of O-H···OH. Raman spectra for all samples have been measured and confirm slight strengthening of the hydrogen bonds with uptake of F. This study discusses the complex crystal chemistry of the skarn mineral rustumite and may provide a wider understanding of the chemical reactions related to contact metamorphism of limestones.

Description: Rauchite, ideally Ni(UO 2 ) 2 (AsO 4 ) 2 ·10H 2 O (IMA no. 2010-037), a new arsenate mineral species of the autunite group, was found at the Belorechenskoye deposit, Adygea Republic, Northern Caucasus, Russia. It is a supergene mineral associated with dymkovite, annabergite and goethite in cavities of a dolomite vein with primary uraninite (pitchblende), nickeline and gersdorffite. Rauchite forms pseudo-tetragonal lamellar crystals (the main form is {001}) up to 0.5 mm across, typically split, like a fan or open book, and their clusters or crusts as large as 2 mm. Rauchite is transparent to translucent and light yellowish-green. The lustre is vitreous. The mineral is brittle, the Mohs’ hardness is ca. 2. The cleavage is {001} perfect. D calc is 3.427 g cm –3 . Rauchite is optically biaxial (–), α = 1.550(3), β = 1.578(1), = 1.581(1), 2 V meas = 40(5)°, 2 V calc = 36°. The average chemical composition (mean of eight electron-microprobe analyses) is (in wt%): MgO = 0.71, CoO = 0.07, NiO = 5.38, ZnO = 0.08, P 2 O 5 = 1.08, As 2 O 5 = 20.26, UO 3 = 54.22, H 2 O calc = 17.10, and the total = 98.90. The empirical formula calculated on the basis of 22 O apfu is: (Ni 0.76 Mg 0.19 Co 0.01 Zn 0.01 ) 0.97 U 2.00 O 4 (As 1.86 P 0.16 ) 2.02 O 8 ·10H 2 O. Rauchite is triclinic, space group I -1, a = 7.100(3), b = 7.125(3), c = 19.955(8) Å, α = 92.406(14), β = 94.924(14), = 90.420(6)°, V = 1004.7(7) Å 3 , Z = 2. [parameters of the reduced P cell are: a = 7.100(3), b = 7.125(3), c = 10.751(4) Å, α = 106.855(7), β = 104.366(7), = 90.420(6)°, V = 502.4(4) Å 3 , Z = 1]. The crystal structure was refined from single-crystal X-ray diffraction data obtained at 153 K ( R 1 = 0.089). The structure is based upon autunite-type [(UO 2 )[AsO 4 ]] – layers with Ni 2+ coordinated by six H 2 O molecules and located in the interlayer space. The strongest lines in the powder X-ray diffraction pattern are [ d in Å( I )( hkl )]: 9.97(100)(002), 6.641(22)(003), 4.936(62)(004, 01-3, –111), 4.533(41)(–112), 3.539(93)(020, 200, 20-1, 01-5, 02-1), 3.388(43)(20-2, 015, 02-2, 105), 2.488(27)(220, 2-21, –125, 1-25, 22-2, –222), and 2.233(27)(1-31, 3-10, 13-1, 31-1, 31-2, 2-24, 13-2, 21-7). The structure of rauchite corresponds to the 1 A -type stacking arrangement of uranyl arsenate layers in the autunite group of minerals and synthetic compounds. The mineral is named in accordance with the naming rules accepted for the autunite group as the hydrated analogue of metarauchite, Ni(UO 2 ) 2 (AsO 4 ) 2 ·8H 2 O.

Description: A new arsenite mineral species dymkovite, ideally Ni(UO 2 ) 2 (As 3+ O 3 ) 2 ·7H 2 O (IMA no. 2010-087), was found at the Belorechenskoye deposit, Adygea Republic, Northern Caucasus, Russia. It is a supergene mineral associated with rauchite, annabergite, and goethite in cavities of a dolomite vein with primary uraninite (pitchblende), nickeline, and gersdorffite. Dymkovite forms long-prismatic, lath-shaped to acicular crystals (≤0.5 mm long, ≤0.05 mm thick), which are elongated along [010]. They are combined in sprays or open-work, chaotic groups up to 1.5 mm across; crusts up to 2 x 2 mm 2 and up to 0.05–mm-thick also occur. Dymkovite crystals are transparent and bright yellow, whereas crusts are translucent and light yellow to light greenish-yellow. The luster is vitreous. The mineral is brittle, the Mohs’ hardness is ca. 3. Cleavage was not observed. D calc is 3.806 g cm –3 . Dymkovite is optically biaxial (–), α = 1.625(2), β = 1.735(5), = 1.745(3), 2 V meas = 20(10)°, 2 V calc. = 32°. Dispersion is strong, r 〉 v . Pleochroism is strong: X = very pale yellowish-green, Y Z = light greenish yellow. In the IR spectrum, bands of As 3+ O 3 anions are strong, whereas bands of As 5+ O 4 anions are very weak. The average chemical composition (electron microprobe) is (in wt%): MgO = 1.11, FeO = 0.24, NiO = 5.40, ZnO = 0.23, As 2 O 3 = 19.57, P 2 O 5 = 0.58, UO 3 = 59.43, H 2 O calc = 13.44, total = 100.00. The empirical formula, calculated on the basis of 17 O apfu, is: (Ni 0.69 Mg 0.26 Fe 0.03 Zn 0.03 ) 1.01 U 1.97 (As 3+ 1.88 P 0.08 ) 1.96 O 9.94 ·7.06H 2 O. Dymkovite is monoclinic, space group C 2/ m , a = 17.99(3), b = 7.033(7), c = 6.633(9) Å, β = 99.62(11)°, V = 827(3) Å 3 , Z = 2. The crystal structure was refined from single-crystal X-ray diffraction data ( R 1 = 0.063). The structure is based upon the [(UO 2 )(As 3+ O 3 )] – sheets formed by chains of edge-sharing [UO 7 ] pentagonal bipyramids and (As 3+ O 3 ) triangular pyramids, which are linked through hydrogen bonds involving disordered [Ni(H 2 O) 6 ] 2+ octahedra and additional H 2 O molecules in the interlayer. The strongest lines of the powder X-ray pattern [ d in Å ( I )( hkl )] are: 8.93(100)(200), 4.463(34)(111, 400), 3.523(23)(020), 3.276(21)(220), 3.008(26)(11-2), 2.846(27)(112, 221, 31-2). Dymkovite is a Ni-dominant, almost arsenate-free analogue of seelite, Mg(UO 2 ) 2 [(As 3+ O 3 ) 1.4 (As 5+ O 4 ) 0.6 ]·7H 2 O. The mineral is named in honor of the Russian mineralogist Yuriy Maksimovich Dymkov (b. 1926), a specialist in U mineralogy, the geology of U deposits, and problems of mineral formation, who was one of the first researchers of the U ores of the Belorechenskoye deposit.

Description: In addition to spurrite, Ca5(SiO4)2(CO3), and tilleyite, Ca5(Si2O7)(CO3)2, galuskinite, Ca7(SiO4)3(CO3), is the third mineral in the CaO-SiO2-CO2 ternary system. Galuskinite, monoclinic, space group P21/c (a = 18.79, b = 6.72, c = 10.47 A, {beta} = 90.79{degrees}, V = 1322 A3, Z = 4), occurs in thin veins which cut calcio-olivine, {gamma}-Ca2SiO4, skarn with larnite, {beta}-Ca2SiO4, relics. Pavlovskyite, Ca8(SiO4)2(Si3O10), and dellaite, Ca6(Si2O7)(SiO4)(OH)2, form a margin between the veins and the calcio-olivine skarn. The sanidinite facies high-temperature skarn formed [~]500 Ma ago when gabbroid rocks of the Birkhin complex (Baikal area, Eastern Siberia, Russia) intruded and contact-metamorphosed limestone xenoliths. Galuskinite is a retrograde product of skarn alteration and has neither been described from cement clinker production processes nor from studies of the CaO-SiO2-CO2 system. The crystal structure of galuskinite, refined from single crystal X-ray data to R1 = 3.1%, has a modular character. One may define a polysomatic series with spurrite and larnite as endmembers and galuskinite as a 1:1 polysome built from regular alternating spurrite and larnite modules. Differences between the X-ray powder patterns of galuskinite and spurrite are most obvious in the low {theta} region. Galuskinite is named after the Russian mineralogists Irina O. Galuskina and Evgeny V. Galuskin, Faculty of Earth Sciences, University of Silesia, Poland, for their outstanding contributions to skarn mineralogy.

Description: Hielscherite, ideally Ca3Si(OH)6(SO4)(SO3)·11H2O, (IMA 2011-037) is the first ettringite-group mineral with essential sulfite. We have identified a continuous natural solid-solution series from endmember thaumasite, Ca3Si(OH)6(SO4)(CO3)·12H2O, to a composition with at least 77 mol.% endmember hielscherite. In this series, the SO3:CO3 ratio is variable, whereas the SO4 content remains constant. Compositions with more than 50 mol.% endmember hielscherite have only been found at Graulay quarry near Hillesheim in the western Eifel Mountains, Rhineland-Palatinate, where they occur with phillipsite-K, chabazite-Ca and gypsum in cavities in alkaline basalt. Sulfite-rich thaumasite has been found in hydrothermal assemblages in young alkaline basalts in two volcanic regions of Germany: it is widespread at Graulay quarry and occurs at Rother Kopf, Schellkopf and Bellerberg quarries in Eifel district; it has also been found at Zeilberg quarry, Franconia, Bavaria. Hielscherite forms matted fibrous aggregates up to 1 cm across and groups of acicular to prismatic hexagonal crystals up to 0.3 × 0.3 × 1.5 mm. Individual crystals are colourless and transparent with a vitreous lustre and crystal aggregates are white with a silky lustre. The Mohs hardness is 2–2½. Measured and calculated densities are Dmeans = 1.82(3) and Dcalc = 1.79 g cm−3. Hielscherite is optically uniaxial (−), ω = 1.494(2), ε = 1.476(2). The mean chemical composition of holotype material (determined by electron microprobe for Ca, Al, Si, and S and gas chromatography for C, H and N, with the S4+:S6+ ratio from the crystal-structure data) is CaO 27.15, Al2O3 2.33, SiO2 7.04, CO2 2.71, SO2 6.40, SO3 12.91, N2O5 0.42, H2O 39.22, total 98.18 wt.%. The empirical formula on the basis of 3 Ca atoms per formula unit is Ca3(Si0.73Al0.28)Σ1.01(OH)5.71(SO4)1.00(SO3)0.62(CO3)0.38(NO3)0.05·10.63H2O. The presence of sulfite was confirmed by crystal-structure analysis and infrared and X-ray absorption near edge structure spectra. The crystal structure of sulfite-rich thaumasite from Zeilberg quarry was solved by direct methods based on single-crystal X-ray diffraction data (R1 = 0.064). The structure of hielscherite was refined using the Rietveld method (Rwp = 0.0317). Hielscherite is hexagonal, P63, a = 11.1178(2), c = 10.5381(2) Å, V = 1128.06(4) Å3 and Z = 2. The strongest reflections in the X-ray powder pattern [(d,Å(I)(hkl)] are: 9.62(100)(010,100); 5.551(50)(110); 4.616(37)(012,102); 3.823(64)(112); 3.436(25)(211), 2.742(38)(032,302), 2.528(37)(123,213), 2.180(35)(042,402;223). In both hielscherite and sulfite-rich thaumasite, pyramidal sulfite groups occupy the same site as trigonal carbonate groups, with analogous O sites, whereas tetrahedral sulfate groups occupy separate positions. Hielscherite is named in honour of the German mineral collector Klaus Hielscher (b. 1957).

Description: Members of the edgrewite Ca 9 (SiO 4 ) 4 F 2 -hydroxyledgrewite Ca 9 (SiO 4 ) 4 (OH) 2 series, structural analogues of clinohumite-hydroxylclinohumite series, Mg 9 (SiO 4 ) 4 (F,OH) 2 , were discovered in xenoliths of carbonate-silicate rock altered to skarn within ignimbrites of the Upper Chegem volcanic structure, Kabardino-Balkaria, Northern Caucasus, Russia. The new minerals occur sparingly in zones containing bultfonteinite, hillebrandite, jennite, and chegemite, as well as rare relics of larnite and rondorfite enclosed in a matrix of hydroxylellestadite. Edgrewite and hydroxyledgrewite are largely altered to jennite in places with admixed zeophyllite and trabzonite, and are preserved as elongate relics mostly 0.1–0.4 mm long in the central part of atoll-like pseudomorphs. The new minerals form a solid-solution series Ca 9 (SiO 4 ) 4 (F,OH) 2 , in which the content of the edgrewite end-member Ca 9 (SiO 4 ) 4 F 2 ranges from 74% (F = 3.64 wt%) to 31% (F = 1.52 wt%). Structure refinement of crystals containing 51% and 37% of the edgrewite end-member gave, respectively, R 1 = 3.03%, space group P 2 1 / b 11 (no. 14), Z = 2, a = 5.06870(10), b = 11.35790(10), c = 15.4004(2) Å, α = 100.5980(10)°, V = 871.47(3) Å 3 ; and R 1 = 1.61%, space group P 2 1 / b 11 (no. 14), Z = 2, a = 5.06720(10), b = 11.35450(10), c = 15.3941(2) Å, α = 100.5870(10)°, and V = 870.63(2) Å 3 . Minerals of the edgrewite-hydroxyledgrewite series are colorless, optically biaxial (+), 2 V meas = 80(5)°; 2 V calc = 78.7°; dispersion r 〉 v , medium; orientation: Z = a , X ^ c = 12(2)°; edgrewite: α = 1.621(2), β = 1.625(2), = 1.631(2); hydroxyledgrewite: α = 1.625(2), β = 1.629(2), = 1.635(2) (589 nm). The micro-hardness VHN 50 = 352–366 kg/mm 2 corresponds to the Mohs scale of 5.5–6. 5. FTIR spectra of edgrewite and hydroxyledgrewite show resolved bands at (edgrewite/hydroxyledgrewite, cm –1 ): 3558 and 3551 and 3543/3554, absent/3486, 1075/1075, 996/996, 980/982, 934/933, 917/918, 904/903, 890/884, 864/864, 842/842, 818/820. Raman spectra are characterized by the following bands (edgrewite/hydroxyledgrewite, cm –1 ) at: 921/923, 889/890, 839/840, and 815/814 (SiO 4 stretching), at: 556/559, 527/527, 423/419, 406/404, and 394/394 (SiO 4 bending), 309/295, 269/256, and 163/166 (CaO 6 ). In the OH stretching region three bands are noted at 3554, 3547, and 3540 cm –1 for edgrewite and two – 3550 and 3475 cm –1 for hydroxyledgrewite confirming the corresponding IR spectra. The major difference in Raman and IR spectra of edgrewite and hydroxyledgrewite is the presence of two resolved peaks in the OH stretching region at ca. 3550 and 3480 cm –1 for hydroxyledgrewite.

Description: Eltyubyuite (IMA2011-022), ideally Ca 12 Fe 3+ 10 Si 4 O 32 Cl 6 i.e . the Fe 3+ analogue of wadalite, Ca 12 Al 10 Si 4 O 32 Cl 6 , was discovered in altered silicate-carbonate xenoliths in the diatreme facies of ignimbrites in the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus, Russia. Eltyubyuite forms light-brown or yellow crystals with tetrahedral habit up to 10 μm across in rondorfite or larnite grains and commonly overgrows wadalite. Associated minerals are hydroxylellestadite, edgrewite-hydroxyledgrewite, chegemite-fluorchegemite, cuspidine, lakargiite, perovskite, kerimasite, srebrodolskite and dovyrenite. Eltyubyuite formed by contact metamorphism of calcareous sediments under sanidinite-facies conditions ( T 〉 800°C, P 〈1–2 kbar). Electron microprobe analysis (mean of 9 points) gave in weight% (s.d.): SiO 2 9.57(0.32), TiO 2 0.48(0.27), Al 2 O 3 3.45(1.81), MgO 0.08(0.07), CaO 36.84(0.91), Fe 2 O 3 , Cl 9.60(0.48); O = Cl –2.13, Sum 98.26, and an empirical formula based on 26 cations, Ca 12.12 Mg 0.04 Ti 0.11 Fe 9.41 Al 1.26 Si 2.98 O 31.89 Cl 5.04 , which simplifies to Ca 12 (Fe 3+ , Al) 11 Si 3 O 32 Cl 5 . Electron-back-scattered diffraction yields isometric symmetry, space group I d (no. 220), a = 12.20(3) Å, V = 1815.85(9) Å 3 , Z = 2. Calculated density and refractive index are 3.349 g/cm 3 and 1.85, respectively. The main bands in Raman spectra of eltyubyuite are attributed to [Fe 3+ O 4 ] 5– : 700–710 cm –1 (stretching vibrations), 460–470 cm –1 (bending vibrations), whereas bands 〈400 cm –1 are assigned to Ca-O and Ca-[Fe 3+ O 4 ] 5– vibrations. The mineral is named for the Balkarian village Eltyubyu, which is situated near the type locality. Eltyubyuite has subsequently been found in altered xenoliths within volcanic rocks of Eifel, Germany and Kel’ Highland (volcano Shadil-Khokh), Southern Ossetia.

Description: Hielscherite, ideally Ca3Si(OH)6(SO4)(SO3)·11H2O, (IMA 2011-037) is the first ettringite-group mineral with essential sulfite. We have identified a continuous natural solid-solution series from endmember thaumasite, Ca3Si(OH)6(SO4)(CO3)·12H2O, to a composition with at least 77 mol.% endmember hielscherite. In this series, the SO3:CO3 ratio is variable, whereas the SO4 content remains constant. Compositions with more than 50 mol.% endmember hielscherite have only been found at Graulay quarry near Hillesheim in the western Eifel Mountains, Rhineland-Palatinate, where they occur with phillipsite-K, chabazite-Ca and gypsum in cavities in alkaline basalt. Sulfite-rich thaumasite has been found in hydrothermal assemblages in young alkaline basalts in two volcanic regions of Germany: it is widespread at Graulay quarry and occurs at Rother Kopf, Schellkopf and Bellerberg quarries in Eifel district; it has also been found at Zeilberg quarry, Franconia, Bavaria. Hielscherite forms matted fibrous aggregates up to 1 cm across and groups of acicular to prismatic hexagonal crystals up to 0.3 × 0.3 × 1.5 mm. Individual crystals are colourless and transparent with a vitreous lustre and crystal aggregates are white with a silky lustre. The Mohs hardness is 2–2½. Measured and calculated densities are Dmeans = 1.82(3) and Dcalc = 1.79 g cm−3. Hielscherite is optically uniaxial (−), ω = 1.494(2), ε = 1.476(2). The mean chemical composition of holotype material (determined by electron microprobe for Ca, Al, Si, and S and gas chromatography for C, H and N, with the S4+:S6+ ratio from the crystal-structure data) is CaO 27.15, Al2O3 2.33, SiO2 7.04, CO2 2.71, SO2 6.40, SO3 12.91, N2O5 0.42, H2O 39.22, total 98.18 wt.%. The empirical formula on the basis of 3 Ca atoms per formula unit is Ca3(Si0.73Al0.28)Σ1.01(OH)5.71(SO4)1.00(SO3)0.62(CO3)0.38(NO3)0.05·10.63H2O. The presence of sulfite was confirmed by crystal-structure analysis and infrared and X-ray absorption near edge structure spectra. The crystal structure of sulfite-rich thaumasite from Zeilberg quarry was solved by direct methods based on single-crystal X-ray diffraction data (R1 = 0.064). The structure of hielscherite was refined using the Rietveld method (Rwp = 0.0317). Hielscherite is hexagonal, P63, a = 11.1178(2), c = 10.5381(2) Å, V = 1128.06(4) Å3 and Z = 2. The strongest reflections in the X-ray powder pattern [(d,Å(I)(hkl)] are: 9.62(100)(010,100); 5.551(50)(110); 4.616(37)(012,102); 3.823(64)(112); 3.436(25)(211), 2.742(38)(032,302), 2.528(37)(123,213), 2.180(35)(042,402;223). In both hielscherite and sulfite-rich thaumasite, pyramidal sulfite groups occupy the same site as trigonal carbonate groups, with analogous O sites, whereas tetrahedral sulfate groups occupy separate positions. Hielscherite is named in honour of the German mineral collector Klaus Hielscher (b. 1957).