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BARAHONAITE-(Al) AND BARAHONAITE-(Fe), NEW Ca–Cu ARSENATE MINERAL SPECIES, FROM MURCIA PROVINCE, SOUTHEASTERN SPAIN, AND GOLD HILL, UTAH

Joan Viñals^1,, John L. Jambor^2,, Mati Raudsepp², Andrew C. Roberts³, Joel D. Grice⁴, Michael Kokinos⁵ and William S. Wise⁶

¹ Department of Chemical Engineering and Metallurgy, University of Barcelona, Martí i Franquès, 1, E–08028 Barcelona, Spain
² Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
³ Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada
⁴ Canadian Museum of Nature, P.O. Box 3443, Station D, Ottawa, Ontario K1P 6P4, Canada
⁵ 4620 Doe Street, Shingle Springs, California 95682-8478, U.S.A.
⁶ Department of Geological Sciences, University of California, Santa Barbara, California 93106, U.S.A.

E-mail address: jvinalsvinals{at}ub.edu

The new mineral species barahonaite-(Fe) and barahonaite-(Al), simplified as (Ca,Cu,Na,Fe³⁺,Al)₁₂Fe³⁺₂(AsO₄)₈(OH)_x·nH₂O and (Ca,Cu,Na,Al)₁₂Al₂(AsO₄)₈(OH)_x·nH₂O, respectively, occur at the Dolores prospect in Murcia Province, southeastern Spain. Barahonaite-(Al) also occurs at the former Gold Hill mine in Tooele County, Utah. The minerals form beads, coalesced beads, and crusts of submillimetric thickness whose surfaces commonly glisten because of the presence of plates, up to 50 µm in diameter (Utah), and razor-thin, tabular, composite crystals, up to 20 µm long (Spain). Barahonaite-(Al) is pale blue, brittle, transparent to translucent, soft, nonfluorescent, and has a white streak and D_meas 3.03 g/cm³; barahonaite-(Fe) is similar, but is yellow with a greenish tint and has a white to pale yellow streak. Both minerals are readily soluble in 10% HCl. Barahonaite-(Fe) is biaxial negative, 1.664(2), β , 1.677(2), 2V_meas 45–80°; the indices of refraction of barahonaite-(Al) are 1.616(2), 1.622(2). The compositions for barahonaite-(Fe) and barahonaite-(Al) from Spain, as determined with an electron microprobe, are, respectively, Na₂O 2.07, 1.65, MgO 0.14, 0.00, CaO 12.96, 15.71, CuO 12.41, 14.59, Al₂O₃ 1.71, 9.52, Fe₂O₃ 13.78, 0.10, SiO₂ 0.33, 0.14, P₂O₅ 0.42, 0.35, As₂O₅ 41.18, 42.16, SO₃ 0.29, 1.24, Cl 0.91, 0.06, H₂O (by difference) 14.01, 14.49, which correspond to (Ca_4.95Cu_3.34Na_1.43Mg_0.07Fe³⁺_1.70Al_0.72)_12.21 Fe³⁺_2.00[(As_0.96P_0.02S_0.01Si_0.01)O₄]₈[(OH)_6.82Cl_0.55]_7.37·13.2H₂O and to (Ca_5.75Cu_3.77Na_1.09Al_1.84Fe³⁺_0.03)_12.48Al_2.00 [(As_0.94S_0.04P_0.01Si_0.01)O₄]₈ [(OH)_7.95Cl_0.04]_7.99·12.5H₂O for XO₄ = 8. Indexing of the powder-diffraction patterns gave a 10.161(7), b 22.39(2), c 10.545(10) Å, β 93.3(1)° for barahonaite-(Fe), and a 9.964(3), b 22.43(1), c 10.555(6) Å, β 92.76(6)° for barahonaite-(Al). The strongest lines in the powder pattern [d in Å(I)(hkl)] are 22.0(100) (010), 11.2(70)(020), 5.068(20)(200), 3.345(20)(023, 310), 2.763(30)(053), 2.659(20)(72), and 2.541(20)(400) for barahonaite- (Fe), and 22.0(100)(010), 11.16(70)(020), 4.983(50)(200), and 3.333(45)(250,13) for barahonaite-(Al). The compositions and X-ray data suggest a possible overall relationship to the smolianinovite group, and a close relationship between attikaite and barahonaite-(Al). The new name barahonaite-(Fe) honors Antonio Barahona (b. 1937) of Madrid, Spain, who collected the original specimens, and barahonaite-(Al) is the Al-dominant analog of barahonaite-(Fe).

Keywords: barahonaite-(Fe), barahonaite-(Al), new mineral species, arsenates, electron-microprobe compositions, X-ray powder data, smolianinovite group, attikaite, Dolores prospect, Spain, Gold Hill mine, Utah.