New Mineral Names*

Home , Corkite, Fougerite, Germanite, Hidalgoite, Narsarsukite, Renierite

American Mineralogist, Volume 82, pages 1038±1041, 1997

NEW MINERAL NAMES*

JOHN L. JAMBOR,1 NIKOLAI N. PERTSEV,2 AND ANDREW C. ROBERTS3

1Department of Earth Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada 2IGREM RAN, Russian Academy of Sciences, Moscow 10917, Staromonetnii 35, Russia 3Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0G1, Canada

Afanasyevaite, cheso®ite, igumnovite, rhythmite 50.1±51.2 (R2). Indexing of the X-ray powder pattern indi- B.V. Chesnokov (1995) High-temperature chlorosilicate cated trigonal symmetry, space group P3m1, a ϭ 4.249(2), in burned-out mine spoil heaps in the Chelyabinsk coal c ϭ 62.82(5) AÊ . The X-ray powder pattern (27 lines, dif-

basin. Doklady Akad. Nauk, 343(1), 94±95 [English fractometer, CoK␣1 radiation) has strongest lines at translation in Trans. Russ. Acad. Sci., Earth Sci. Sect., 4.50(46,00.14), 3.09(100,01.11), 2.255(38,10.22), and 345(8), 104±106, 1996]. 2.126(25,110). The structure has 33 layers per cell. Electron microprobe analyses (not given, except for Cl The mineral occurs among voids in aggregates of an- and F) are reported to correspond to the following named dradite, calcite, chlorite, and stilpnomelane in altered magnetite-andradite skarn at the Tyrny'auz W-Mo depos- compounds. Afanasyevaite is Ca8[Si2O7]2´Cl2O, granular habit, pseudocubic; electron microprobe analysis gave it, Kabardino-Balkaria Republic, Russian Federation. Baksanite contains inclusions of native gold and, rarely, 6.19 Cl (calc., 9.35 wt%), 0.85 F, and 0.64 SO3 wt%. Cheso®ite is Ca [Si O ] ´CaCl , acicular habit, monoclin- intergrowths of ingodite and joseite-A; all are separated 9 2 7 3 2 from the host aggregates by a thin lining of bismuthinite. ic, Cl 7.33, F 0.04 wt%. Igumnovite is Ca3Al2[SiO4]2Cl4, cubic, Cl 28.25, F 0.13 wt%. Rhythmite is The new name refers to the type locality, the Baksan Riv- er valley. Type material is in the Fersman Mineralogical Ca4[SiO4]2´3CaCl2, orthorhombic, Cl 31.06, F 0.22 wt%. The compounds were formed by the reaction of mudstone Museum, Moscow, Russia. N.N.P. and dolomite, and other carbonate rocks, in burned-out mine wastes from the Kopeysk coal mines in the Chelya- Fougerite binsk basin, southern Urals, Russia. Discussion. Additional data and the derivation of the F. Trolard, M. Abdelmoula, G. BourrieÂ, B. Humbert, J.-M.R. GeÂnin (1996) Evidence of the occurrence of a names are not given. The compounds no longer qualify ``green rusts'' component in hydromorphic soils. Pro- as minerals. J.L.J. posed existence of a new mineral ``fougerite.'' C. Ren- du Acad. Sci. Paris, Ser. IIa, 323, 1015±1022 (in French, English abs.). Baksanite* F. Trolard, J.-M.R. GeÂnin, M. Abdelmoula, G. BourrieÂ, B. I.V. Pekov, E.N. Zav'yalov, S.V. Fedyushchenko, D.K. Humbert, A. Herbillon (1997) Identi®cation of a green Shcherbachev, Yu.S. Borodayev, G.D. Dorokhova rust mineral in a reductomorphic soil by MoÈssbauer and Raman spectroscopies. Geochim. Cosmochim. (1996) Baksanite, Bi6(Te2S3), a new mineral from Tyr- ny'auz (northern Caucasus). Doklady Akad. Sci., Acta, 61, 1107±1111. 347(6), 787±791 (in Russian). So-called green rusts are well known synthetically. It has long been assumed that the same, mixed-valence Electron microprobe analysis of several grains that were Fe2ϩ-Fe3ϩ compound is responsible for the blue-green col- checked by X-ray powder patterns gave a mean of Bi 76.40, ors in sediments and hydromorphic soils that rapidly be- Pb 2.15, Sb 0.12, Te 14.33, Se 0.00, S 6.64, sum 99.64 come ochreous upon exposure to air as a consequence of wt%, corresponding to (Bi Pb Sb ) (Te S ). The 5.78 0.16 0.02 ⌺5.96 1.77 3.27 oxidation of Fe2ϩ and transformation of the blue-green composition is uniform. The mineral occurs as spherical to phase to goethite and lepidocrocite. MoÈssbauer and Ra- droplet-like single grains and aggregates up to 13 mm man spectra, and dissolution by citrate-bicarbonate re- across; steel-gray color, metallic luster, black streak, perfect agent, showed that the natural and synthetic compounds basal cleavage, H ϭ 11 ±2, VHN ϭ 62 (mean for aniso- ⁄2 5 are identical; previous studies had indicated the general tropic sections), D ϭ 8.1(1), D ϭ 8.07 g/cm3 for Z ϭ meas calc formula of the compound to be [Fe2ϩ Fe3ϩ (OH) ]xϩ´ 3. Bright white in re¯ected light, weak bire¯ectance, dis- 1 Ϫ xx 2 [xAϪz´mHO]xϪ, where Fe is in Fe(OH) brucite-like layers tinctly anisotropic in yellowish gray tints; re¯ectance per- ⁄z ⁄z2 2 that alternate with AzϪ anions and H O molecules. The centages, given in 20 nm steps from 400 to 700 nm, range 2 formula can be simpli®ed as Fe2ϩFe3ϩ(OH) . The new from 46.3±48.5 (R , 400 and 700 nm, respectively) and 5 1 name fougerite refers to the locality of the natural sample * Before publication, minerals marked with an asterisk were studied, which was from a soil pro®le at FougeÁres, Brit- approved by the Commission on New Minerals and Mineral tany, France. Names, International Mineralogical Association. Discussion. The authors state that the name fougerite 0003±004X/97/0910±1038$05.00 1038 JAMBOR ET AL.: NEW MINERAL NAMES 1039

has been submitted to the ``IMA Committee,'' but a com- Pr2O3 1.19, Nd2O3 4.26, Y2O3 0.15, CO2 (calc.) 21.95, F plete proposal has not been received by the CNMMN. 3.18, O ϵ F 1.34, sum 100.63 wt%, corresponding to

J.L.J. (Ba1.86Sr0.09Ca0.04)⌺1.99(Ce0.56La0.24Nd0.15Pr0.04Y0.01)⌺1.00(CO3)3F1.01. Occurs as prismatic, bladed crystals, up to 1.0 mm long, commonly as dendritic or stellate groups, 2±3 mm across. Gallobeudantite* Color yellow, white, or pinkish gray, white streak, transpar- J.L. Jambor, D.R. Owens, J.D. Grice, M.N. Feinglos ent, vitreous to greasy luster, cleavage not observed, brittle, uneven fracture, VHN ϭ 280(25), H ϭ 4.5, D ϭ 4.7(1), (1996) Gallobeudantite, PbGa3[(AsO4),(SO4)]2(OH)6,a 25 meas 3 new mineral species from Tsumeb, Namibia, and as- Dcalc ϭ 4.62 g/cm for Z ϭ 2; effervesces in HCl, non¯u- sociated new gallium analogues of the alunite-jarosite orescent. The infrared spectrum has strong absorption bands family. Can. Mineral., 34, 1305±1315. at 1600±1200, 1100±1060, 900±850, and 745±675 cmϪ1. Optically biaxial negative, ␣ϭ1.584(1), ␤ϭ1.724(3), ␥ One representative electron microprobe analysis (of ϭ 1.728(3), 2V ϭ 16(1)Њ,2V ϭ 18Њ, Z c ϭ 26.5Њ in eight) gave PbO 32.1, ZnO 2.2, Ga O 19.2, Fe O 2.9, meas calc ٙ 2 3 2 3 obtuse ␤, medium dispersion r Ͼ v, Y ϭ b. Single-crystal Al O 8.9, As O 16.0, SO 10.5, P O 0.2, GeO 0.6, H O 2 3 2 5 3 2 5 2 2 X-ray study indicated monoclinic symmetry, space group 8.3 (from stoichiometry and crystal-structure analysis), P2 /m, a ϭ 13.396(7), b ϭ 5.067(1), c ϭ 6.701(1) AÊ , ␤ϭ sum 100.9 wt%, corresponding to Pb (Ga Al Fe3ϩ 1 1.00 1.43 1.21 0.25 106.58(1)Њ. Strongest lines of the powder pattern are 4.00 Zn Ge ) [(AsO ) (SO ) (PO ) ] (OH) , ide- 0.19 0.04 ⌺3.12 4 0.96 4 0.91 4 0.02 ⌺1.89 6.41 (100,111,201), 3.269(100,310,202,401), 2.535(20,020, ally PbGa[(AsO ),(SO )] (OH) . This is the Ga analog of 4 4 2 6 112), 2.140(40,221,003,512,600), and 2.003(40, several). beudantite, idealized as PbFe3ϩ [(AsO )(SO )] (OH) . Oc- 3 4 4 2 6 The new name is for A.A. Kukharenko (1914±1993), curs as zones within rhombohedra, up to 200 ␮m along in recognition of his contributions to the geology of the an edge, in vugs in a single specimen of Cu-bearing sul- Kola Peninsula. The mineral occurs in carbonatites and ®des (renierite, germanite-like, tennantite, and secondary zeolite-carbonate rocks in the Khibina and VuorijaÈrvi al- chalcocite). Crystals are variably pale yellow, greenish, kaline massifs, Kola Peninsula, Russia, in a hornfels xe- or cream-colored; white to pale yellow streak, vitreous nolith at Mont Saint Hilaire, QueÂbec, and in cavities in luster, even to conchoidal fracture, H ϭ 4, transparent, the Saint-Amable sill, a nepheline syenite related to the brittle, non¯uorescent, possible {001} cleavage, D ϭ calc Mont Saint Hilaire alkaline intrusions. Type material is 4.61 g/cm3 for Z ϭ 3. Optically nonpleochroic, uniaxial in the Mineralogical Museum of the Department of Min- negative, ␻ϭ1.763(5), ⑀ϭ1.750(5). Single-crystal eralogy, Saint Petersburg University, Russia, and in the X-ray structure study (R ϭ 0.078) indicated hexagonal Canadian Museum of Nature, Ottawa. J.L.J. (rhombohedral) symmetry, space group R3m, a ϭ 7.225(4), c ϭ 17.03(2) AÊ , isostructural with corkite. Strongest lines of the 114.6 mm Debye±Scherrer powder NezÏilovite* pattern (CoK radiation) are 5.85(90)(101), 3.59(40)(110), ␣ V. Bermanec, D. Holtstam, D. Sturman, A.J. Criddle, 3.038(100)(113), and 2.271(40)(107). M.E. Back, S. SÏcÂavnicÏar (1996) NezÏilovite, a new The zoned crystals also contain Ga-rich beudantite and member of the magnetoplumbite group, and the crystal hidalgoite, and the unnamed Ga analogs of segnitite, chemistry of magnetoplumbite and hibonite. Can. Min- corkite, kintoreite, and arsenocrandallite. In addition, he- eral., 34, 1287±1297. matite, goethite, stolzite, mercurian silver, and otjisumeite Electron microprobe analysis gave PbO 19.01, CaO 0.03, have been identi®ed on the holotype specimen from Tsu- Sb O 0.25, ZnO 13.23, Fe O 41.96, Mn O 7.13, MnO meb, Namibia. The name alludes to the predominance of 2 5 2 3 2 3 2 11.01, TiO 2.84, Al O 4.52, MgO 0.08, sum 100.06 wt%, Ga in the position occupied by Fe3ϩ in beudantite-type 2 2 3 corresponding to Pb Ca Sb Zn Fe3ϩ Mn3ϩ Mn4ϩ Ti minerals. Type material (polished section of sul®de-rich 0.99 0.01 0.02 1.89 6.11 1.05 1.74 0.41 Al Mg , ideally PbZn (Mn4ϩ,Ti4ϩ)Fe3ϩ O . The mineral matrix and sections of analyzed grains) is in the System- 1.03 0.02 2 2 8 19 occurs as black, magnetic, thin tabular {0001} crystals that atic Reference Series of the National Mineral Collection, are hexagonal in outline and up to 1 mm across. Dark brown housed at the Geological Survey of Canada, Ottawa. The to nearly black streak, opaque, no internal re¯ection, prom- crystal used for structure determination is in the Canadian inent {0001} cleavage, VHN ϭ 735 (599±847), D ϭ Museum of Nature, Ottawa. A.C.R. 25 calc 5.69 g/cm3 for Z ϭ 2. In re¯ected light, anisotropic and bire¯ectant, nonpleochroic. Re¯ectance values are given in 20 nm steps from 400 to 700 nm; standard values in air and Kukharenkoite-(Ce)* in oil are, respectively, 23.8, 10.0 (470), 22.4, 8.8 (546), A.N. Zaitsev, V.N. Yakovenchuk, G.Y. Chao, R.A. Gault, 21.7, 8.3 (589), and 20.7, 7.7 (650). Single-crystal X-ray V.V. Subbotin, Y.A. Pakhomosky, A.N. Bogdanova structure study (R ϭ 0.045) indicated hexagonal symmetry, (1996) Kukharenkoite-(Ce), Ba Ce(CO ) F, a new min- 2 3 3 space group P6 /mmc, a ϭ 5.849(1), c ϭ 22.809(2) AÊ . eral from Kola Peninsula, Russia, and QueÂbec, Canada. 3 Eur. J. Mineral., 8, 1327±1336. Strongest lines of the powder pattern are 11.39(45,002), 3.811(100,006), 2.858(75,008), 2.745(50,107), and 2.605 The average of 12 electron microprobe analyses gave (40,114).

CaO 0.39, SrO 1.55, BaO 47.39, La2O3 6.61, Ce2O3 15.30, The mineral occurs in marble in the Precambrian Pe- 1040 JAMBOR ET AL.: NEW MINERAL NAMES lagonian massif in the NezÏilovo area of Macedonia. Type Strange Lake deposit, Quebec±Labrador. Can. Miner- material is in the Natural History Museum at Zagreb, al., 34, 1299±1304. Croatia, in the Royal Ontario Museum, Toronto, and in Electron microprobe analysis (average of seven grains) the Swedish Museum of Natural History, Stockholm. gave Na 6.4, Ca 11.5, Y 2.2, La 11.3, Ce 22.0, Nd 8.0, J.L.J. Sm 1.1, Gd 2.9, Dy 0.4, F 35.4, sum 101.2 wt%, corre-

sponding to Na0.90[(REE)1.12Ca0.92]⌺2.04F6, wherein Ce is the predominant REE. The simpli®ed formula is Piretite* Na(REE,Ca)2F6. Occurs as colorless to pale pink anhedral R. Vochten, N. Blaton, O. Peeters, M. Deliens (1996) xenomorphic grains, 1±2 mm across; vitreous luster, Piretite, Ca(UO2)3(SeO3)2(OH)4´4H2O, a new calcium white streak, conchoidal fracture, transparent, brittle, non- uranyl selenite from Shinkolobwe, Shaba, Zaire. Can. ¯uorescent, H ϭ 3½, slowly soluble in hot HCl, Dmeas ϭ Mineral., 34, 1317±1322. 3 4.44(1), Dcalc ϭ 4.55 g/cm for Z ϭ 3. Optically uniaxial Electron microprobe analysis of ®ve crystals gave CaO positive, ⑀ϭ1.483(1), ␻ϭ1.503(1), nonpleochroic. Sin- gle-crystal X-ray structure study indicated hexagonal (tri- 3.57, UO3 72.00, SeO2 19.29, H2O (TGA) 8.00, sum 102.86, gonal) symmetry, space group P3, a ϭ 6.099(1), c ϭ corresponding to Ca0.76(UO2)3.02(SeO3)2.09(OH)3.38´3.64H2O. Occurs as lemon-yellow elongate tablets, irregular in outline 11.064 AÊ as re®ned from a 114.6 mm Gandol® pattern and up to 1 ϫ 3 mm, ¯attened on (001), showing {100}, with strongest lines of 5.29(70,100), 3.036(100,110,103), {010}, and {001}; also as acicular prisms to 5 mm. Pale 2.146(70,203), 1.757(80,300,213), 1.152(40,410), and yellow streak, transparent to translucent, pearly luster, 0.9189(40,513). good {001} cleavage, uneven fracture, H ϭ 2.5, non¯u- The mineral occurs sparingly disseminated in hyper- 3 solvus granite at the Strange Lake Zr-Y-REE-Nb-Be de- orescent, Dmeas ϭ 4.00, Dcalc ϭ 3.87 g/cm for Z ϭ 4. The infrared spectrum has absorption bands at 3303, 2927, posit, on the QueÂbec±Labrador boundary, northeast of Ϫ1 Ϫ1 Shefferville, QueÂbec. Associated minerals include vlasov- and 1623 cm for H2O, at 898 cm for UO2, and at 815, Ϫ1 ite, narsarsukite, willemite, ¯uorite, and bastnaÈsite-(Ce), 732, and 468 cm for SeO3. Optically biaxial negative, the last as an alteration of zajacite-(Ce). The new name ␣calc ϭ 1.54, ␤ϭ1.73(1), ␥ϭ1.75(1), 2V ϭ 33(5)Њ, weak dispersion r Ͼ v, X ࿣ c, Y ࿣ a, Z ࿣ b. Single-crystal X-ray is for geologist Ihor Stephan Zajac, who led the explo- ration group that discovered the Strange Lake deposit, study indicated orthorhombic symmetry, space group Pmn21 or Pmnm; a ϭ 7.010(3), b ϭ 17.135(7), c ϭ 17.606(4) AÊ and who ®rst recognized the presence of the new mineral. Type material is in the Systematic Reference Series of the as re®ned from a Guinier-HaÈgg pattern (CuK␣1 radiation) with strongest lines of 8.79(80,002), 8.56(40,020), National Mineral Collection, housed at the Geological 4.30(30,131), 3.51(100,200), 3.032(100,151), and 1.924 Survey of Canada, Ottawa. A.C.R. (40,237). The mineral occurs in association with a masuyite-like PdSn ,PdSe U-Pb oxide as crusts on uraninite from the U deposit at 2 3 2 Shinkolobwe. The name is for Paul Piret, University of N.S. Rudashevskiy, V.V. Knauf, N.M. Chernyshov (1995) Louvain-la-Neuve, Belgium. Type material is in the Roy- Platinum-group minerals from Kursk magnetic anom- al Belgian Institute of Natural Sciences, Brussels. J.L.J. aly black shales. Doklady Akad. Sci., 344(1), 91±95 [English translation in Trans. Russ. Acad. Sci., Earth Sci. Sect., 345(9), 243±249, 1996]. Wadsleyite II Energy dispersion analysis of grains, up to 15 ϫ 30 J.R. Smyth, T. Kawamoto (1997) Wadsleyite II: A new ␮m, that surround a platelet of native palladium gave Pd 31.1, Sn 68.6, sum 99.7 wt%, corresponding to high pressure hydrous phase in the peridotite±H2O system. Earth Planet. Sci. Lett., 146, E9±E16. Pd1.00Sn2.00. A Pd-Se mineral occurs as rounded grains, up to 20 ϫ 30 ␮m, and as isolated, zoned, individual crystals An orthorhombic compound of composition to 1 ϫ 6 ␮m. Analysis of the cores gave Pd 49.4, Pt 20.0, Mg1.71Fe0.177Al0.01Si0.965H0.332O4 synthesized at 1400 ЊC has Fe 0.6, Se 30.9, sum 100.9 wt%, corresponding to a ϭ 5.6884, b ϭ 28.9238, c ϭ 8.2382 AÊ , with a and c (Pd2.39Pt0.53Fe0.06)⌺2.98Se2.02, and analysis of the rims gave Pd 2ϩ approximating those of wadsleyite, ␤-(Mg,Fe )2SiO4, but 63.3, Pt 4.0, Fe 0.7, Se 32.1, sum 100.1 wt%, correspond- with b ϭ 2.5ϫ that of wadsleyite. ing to (Pd2.87Pt0.10Fe0.06)⌺3.03Se1.97. Only the PdSn2 mineral Discussion. Although the authors have not chosen a has a synthetic counterpart. The Pd minerals are associ- trivial name for the synthetic phase, such compounds do ated with sul®des, mainly pyrite and pyrrhotite, in car- not qualify as minerals and should not be assigned min- bonaceous Precambrian black shales in the Voronezh eral names. J.L.J. crystalline massif, Voronezh±Kursk area, Russia. J.L.J.

Zajacite-(Ce)* Ag2Pb3Bi2S7 J.L. Jambor, A.C. Roberts, D.R. Owens, J.D. Grice (1996) G.V. Moralev, V.I. Milyayev (1994) Bismuth mineraliza- Zajacite-(Ce), a new rare-earth ¯uoride from the tion and vertical zoning in the Shkol'noye gold-silver JAMBOR ET AL.: NEW MINERAL NAMES 1041

deposit, Kuraminskiy Range, northern Tajikistan. Dok- plete ordering lowers the symmetry and distinguishes the lady Akad. Nauk, 338(6), 802±805 (English translation mineral from others in the hydrotalcite-manasseite series. in Trans. Russ. Acad. Sci., Earth Sci. Sect., 345, 138± The mineral occurs in dolomitic carbonatite at the Jacu- 143, 1996). piranga massif, San Paulo, Brazil. Electron microprobe analysis gave Pb 40.51, Cu 0.16, Discussion. See also the abstracts for mineral IMA 92± Ag 14.16, Au 0.13, Fe 0.07, Zn 0.10, Sb 0.72, As 1.30, 028 and 92±029, which are closely related and have the Bi 26.41, Se 1.97, S 14.11, sum 100.80 wt%; after de- same formula. N.N.P duction of Fe and Zn (and Si), the formula corresponds to (Ag,Au,Cu)2.03Pb2.94(Bi,As,Sb)2.25(S,Se)7.01, ideally Ag2

Pb3Bi2S7. The grains are Ͻ30 ␮m and are associated with argentian tetrahedrite, polybasite, chalcopyrite, galena, New Data native bismuth, and argentian gold in quartz-carbonate Malladrite veins. J.L.J. E.K. Sera®mova, T.F. Semenova, L.P. Vergasova, S.K. Fi- latov, V.B. Epifanova, V.V. Anan'yev (1996) New data

on malladrite Na2SiF6, a mineral of volcanic exhala- Tetragonal (Zn,Mn)Fe2O4 tions from the Large Tolbachik Fissure Eruption. Vol- J.R. Marcano, A.E. Mora, O. Odreman, J.M. Delgado canol. Seismol., (1), 46±55 (in Russian). (1996) Single-crystal structural study of a natural (Zn,Mn) ferrite. Materials Research Bull., 31(12), Ten electron microprobe analyses gave a mean and 1587±1592. range of Na 25.59 (25.26±26.37), K 0.04 (0.02±0.05), Si 14.58 (14.38±14.83), F 60.62 (59.90±61.20), sum 100.83 Energy dispersion analysis of a dark single-crystal (99.71±101.99) wt%, corresponding to Na2.05Si0.98F6. Oc- fragment from a mine in the Bailadores region, MeÂrida, curs as colorless to white tablets up to 0.5 mm across and Venezuela, gave an atomic ratio of Zn:Mn:Fe ϭ 1:1:2. Sin- 0.2 mm thick, showing {0001}, {1120}, and {1010}. Vit- gle-crystal X-ray structure study (R ϭ 0.0170) indicated te- reous to greasy luster, perfect {0001} cleavage, VHN10-20 tragonal symmetry, space group I41/amd, a ϭ 5.964(2), c ϭ 3 ϭ 78±84 on (0001), Hcalc ϭ 2.9, Dcalc ϭ 2.756 g/cm for Ê 3 8.449(3) A, Dcalc ϭ 5.275 g/cm for Z ϭ 4. The cation dis- Z ϭ 3. Solubility 5.7, 9.9, and 24.6 g/L at 15, 40, and tribution re®ned to [Zn0.74Fe(Mn)0.26][Zn0.01Fe(Mn)1.99]O4. 100 ЊC, respectively. Optically uniaxial negative, n ϭ Discussion. Details about the properties and processing Ͻ1.33. Trigonal symmetry, space group P3m1orP321, history of the sample are not given. J.L.J. a ϭ 8.859(1), c ϭ 5.040(1) AÊ . Strongest lines of the powder pattern (diffractometer, CuK␣ radiation, 40 lines given) are 4.426(67,110), 4.210(70,101), 3.325(80,111), Al2Mg4(OH)12(CO3)´3H2O 3.053(67,201), 2.281(100,301), and 1.795(78,302), in

A.V. Arakcheyeva, D.Yu. Pushcharovskii, R.K. Rastsvetae- good agreement with data for synthetic Na2SiF6. va, D. Atencio, G.U. Lubman (1996) Crystal structure The mineral occurs in an open ®ssure at the edge of a and comparative crystallochemistry of Al2Mg4(OH)12 northern crater of the Large Tolbachik Fissure Eruption, (CO )´3H O, a new mineral in the hydrotalcite-manasseite 3 2 Kamchatka, Russia, and constitutes up to 19 wt% of group. Kristallogra®ya, 41(6), 1024±1034 (in Russian). white and brownish white exhalation crusts of gypsum, The mineral occurs as bright orange-red grains, 2±6 possibly anhydrite, and minor unidenti®ed complex ¯u- mm across, with a hexagonal trapezoidal habit, and pris- orides. Malladrite was found in 1985, when the walls of matic and basal pinacoidal modi®cations. Perfect pina- the ®ssure were at 60 ЊC and temperatures of the fuma- coidal cleavage. Single-crystal X-ray structure study (R rolic gases were Ͻ100 ЊC. In 1988 and 1989, when tem- ϭ 0.039) indicated hexagonal symmetry, space group peratures were higher, the amount of malladrite decreased P62m, a ϭ 5.283(3), c ϭ 15.150(9) AÊ . Within the struc- in the exhalations. ture is (1) a brucite-type layer [AlMg2(OH)6], (2) a car- Discussion. The description adds to the previously in- bonate [CO3] net, and (3) a net of [3H2O]; these three complete data for the physical properties of the mineral. structural elements have the sequence 1±2±1±3±1. Com- N.N.P.