- © 2008 American Mineralogist
Barahonite-(Fe) and barahonite-(Al)*
J. Viñals, J.L. Jambor, M. Raudsepp, A.C. Roberts, J.D. Grice, M. Kokinos, and W.S. Wise (2008) Barahonaite-(Al) and barahonaite-(Fe), new Ca-Cu arsenate mineral species from Murcia province, Southeastern Spain, and Gold Hill, Utah. Can. Mineral., 46, 205–217.
Barahonite-(Fe) and barahonite-(Al) were found at the Dolores prospect near Pastrana, Murcia province, northern Spain. Barahonite-(Al) is also found at the Gold Hill Mine in Toole County, western Utah. At the Dolores prospect, the new minerals occur in a small lens of sulfides that have been completely oxidized to an assembly of 25 supergene minerals. Associated minerals include arsenocrandallite, arsenogoyazite, conichalcite, cobaltarthurite, chlorargyrite, olivenite, azurite, cornwallite, pharmacosiderite, zálesíite, and lavendulan. At the Gold Hill mine, primary sulfides have been oxidized to arsenate and sulfate assemblages.
Barahonaite-(Fe) typically occurs as isolated beads (rosettes) forming sparse coatings on pharmacosiderite in fracture surfaces. The beads commonly coalesce. Barahonaite-(Al) from the Dolores prospect has a similar habit but is sparser. SEM imaging shows that these beads consist of thin tabular composite crystals with a maximum length of 20 μm. Barahonaite-(Al) from Gold Hill is rare but more common than at Dolores. It forms thin sub-millimeter crusts on weathered fracture surfaces. These crusts commonly form on a nearly amorphous Al silicate. Barahonaite-(Fe) is greenish-yellow and has a white to pale yellow streak, whereas barahonaite-(Al) is pale blue with a white streak. Both minerals are transparent to translucent, non-fluorescent, have a vitreous luster, are brittle, and are easily dissolved by room-temperature 10% HCl. Measured density for the Utah barahonaite is 3.03 g/cm3 while Dcalc = 2.99 g/cm3 for Z = 2. Barahonaite-(Fe) is biaxial negative, α = 1.664(2), β γ, γ = 1.677(2), 2Vmeas = 45–80°; the indices of refraction of barahonaite-(Al) are α = 1.616(2), γ = 1.622(2). Barahonaite-(Al) is presumed to …