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

Abstract

The new mineral species barahonaite-(Fe) and barahonaite-(Al), simplified as (Ca,Cu,Na,Fe 3+ ,Al) 12 Fe 3+ 2 (AsO 4 ) 8 (OH) x · n H 2 O and (Ca,Cu,Na,Al) 12 Al 2 (AsO 4 ) 8 (OH) x · n H 2 O, 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/cm 3 ; 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, α 1.664(2), β ≈ γ, γ 1.677(2), 2 V meas 45–80°; the indices of refraction of barahonaite-(Al) are α 1.616(2), γ 1.622(2). The compositions for barahonaite-(Fe) and barahonaite-(Al) from Spain, as determined with an electron microprobe, are, respectively, Na 2 O 2.07, 1.65, MgO 0.14, 0.00, CaO 12.96, 15.71, CuO 12.41, 14.59, Al 2 O 3 1.71, 9.52, Fe 2 O 3 13.78, 0.10, SiO 2 0.33, 0.14, P 2 O 5 0.42, 0.35, As 2 O 5 41.18, 42.16, SO 3 0.29, 1.24, Cl 0.91, 0.06, H 2 O (by difference) 14.01, 14.49, which correspond to (Ca 4.95 Cu 3.34 Na 1.43 Mg 0.07 Fe 3+ 1.70 Al 0.72 ) ∑12.21 Fe 3+ 2.00 [(As 0.96 P 0.02 S 0.01 Si 0.01 )O 4 ] 8 [(OH) 6.82 Cl 0.55 ] ∑7.37 ·13.2H 2 O and to (Ca 5.75 Cu 3.77 Na 1.09 Al 1.84 Fe 3+ 0.03 ) ∑12.48 Al 2.00 [(As 0.94 S 0.04 P 0.01 Si 0.01 )O 4 ] 8 [(OH) 7.95 Cl 0.04 ] ∑7.99 ·12.5H 2 O for X O 4 = 8. Indexing of the powder-diffraction patterns gave a 10.161(7), b 22.39(2), c 10.545(10) A, β 93.3(1)° for barahonaite-(Fe), and a 9.964(3), b 22.43(1), c 10.555(6) A, β 92.76(6)° for barahonaite-(Al). The strongest lines in the powder pattern [ d in A( 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)(172), 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)(250,113) 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).