Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Supplementary Data Info Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Atencio, D. Articles by Möckel, S. Search for Related Content GeoRef GeoRef Citation

Footemineite, the Mn-analog of atencioite, from the Foote mine, Kings Mountain, Cleveland County, North Carolina, U.S.A., and its relationship with other roscherite-group minerals

¹ Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, 05508-080, São Paulo, SP, Brazil
² Museu de Ciências Naturais de Santos Jobas "José Bonifácio de Andrada e Silva"—Largo Marquês de Monte Alegre, 11010-260, Valongo, Centro Histórico, Santos, SP, Brazil
³ 303 Church Street, Belmont, North Carolina 28012-3320, U.S.A.
⁴ Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region 142432, Russia
⁵ Institute of Crystallography, Russian Academy of Sciences, Leninskii Prospekt 59, Moscow 119333, Russia
⁶ Alpha-Geophysik in Sachsen, Neudorfer Str. 18. D-09629, Burkersdorf, Germany

Correspondence: ^* E-mail: datencio{at}usp.br

Footemineite, ideally Ca₂Mn²⁺Mn₂²⁺ Mn₂²⁺ Be₄(PO₄)₆(OH)₄·6H₂O, triclinic, is a new member of the roscherite group. It occurs on thin fractures crossing quartz-microcline-spodumene pegmatite at the Foote mine, Kings Mountain, Cleveland County, North Carolina, U.S.A. Associated minerals are albite, analcime, eosphorite, siderite/rhodochrosite, fairfieldite, fluorapatite, quartz, milarite, and pyrite. Footemineite forms prismatic to bladed generally rough to barrel-shaped crystals up to about 1.5 mm long and 1 mm in diameter. Its color is yellow, the streak is white, and the luster is vitreous to slightly pearly. Footemineite is transparent and non-fluorescent. Twinning is simple, by reflection, with twin boundaries across the length of the crystals. Cleavage is good on {01} and {100}. Density (calc.) is 2.873 g/cm³. Footemineite is biaxial (–), n = 1.620(2), n_β = 1.627(2), n = 1.634(2) (white light). 2V_obs = 80°, 2V_calc = 89.6°. Orientation: X ^ b ~ 12°, Y ^ c ~ 15°, Z ^ a ~ 15°. Elongation direction is c, dispersion: r > v or r < v, weak. Pleochroism: β (brownish yellow) > = (yellow). Mössbauer and IR spectra are given. The chemical composition is (EDS mode electron microprobe, Li and Be by ICP-OES, Fe³⁺: Fe²⁺ by Mössbauer, H₂O by TG data, wt%): Li₂O 0.23, BeO 9.54, CaO 9.43, SrO 0.23, BaO 0.24, MgO 0.18, MnO 26.16, FeO 2.77, Fe₂O₃ 0.62, Al₂O₃ 0.14, P₂O₅ 36.58, SiO₂ 0.42, H₂O 13.1, total 99.64. The empirical formula is (Ca_1.89Sr_0.03Ba_0.02)_1.94(Mn_0.90²⁺_0.10)_1.00 (_0.78Li_0.17Mg_0.05) _1.00(Mn_3.25²⁺Fe_0.43²⁺Fe_0.09³⁺ Al_0.03) _3.80Be_4.30(P_5.81Si_0.08O₂₄)[(OH)_3.64(H₂O)_0.36] _4.00·6.00 H₂O. The strongest reflection peaks of the powder diffraction pattern [d, Å (I, %) (hkl)] are 9.575 (53) (010), 5.998 (100) (01), 4.848 (26) (021), 3.192 (44) (210), 3.003 (14) (02), 2.803 (38) (03), 2.650 (29) (02), 2.424 (14) (231). Single-crystal unit-cell parameters are a = 6.788(2), b = 9.972(3), c = 10.014(2) Å, = 73.84(2), β = 85.34(2), = 87.44(2)°; V = 648.74 ų, Z = 1. The space group is P. Crystal structure was refined to R = 0.0347 with 1273 independent reflections (F > 2). Footemineite is dimorphous with roscherite, and isostructural with atencioite. It is identical with the mineral from Foote mine described as "triclinic roscherite." The name is for the Foote mine, type locality for this and several other minerals.

Key Words: Footemineite • new mineral • roscherite-group • Mn-phosphate • crystal structure • atencioite • Foote mine • North Carolina