Details

Autor(en) / Beteiligte

• Kampf, Anthony R
• Cooper, Mark A
• Celestian, Aaron J
• Ma, Chi
• Marty, Joe

Titel

Dendoraite-(NH4), a new phosphate-oxalate mineral related to thebaite-(NH4) from the Rowley Mine, Arizona, USA

Ist Teil von

• Mineralogical magazine, 2022-08, Vol.86 (4), p.531-538

Ort / Verlag

London: Cambridge University Press on behalf of the Mineralogical Society of the UK and Ireland

Erscheinungsjahr

2022

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Dendoraite-(NH4), (NH4)2NaAl(C2O4)(PO3OH)2(H2O)2, is a new mineral species from the Rowley Mine, Maricopa County, Arizona, USA. It occurs in an unusual bat-guano-related, post-mining assemblage of phases that include a variety of vanadates, phosphates, oxalates and chlorides, some containing NH4+. Other secondary minerals found in association with dendoraite-(NH4) are antipinite, fluorite, mimetite, mottramite, relianceite-(K), rowleyite, salammoniac, struvite, vanadinite, willemite, wulfenite and at least one other new mineral. Crystals of dendoraite-(NH4) are colorless blades up to ∼0.1 mm in length. The streak is white and luster is vitreous, Mohs hardness is 2 1/2, tenacity is brittle and fracture is splintery. The calculated density is 2.122 g·cm-3. Dendoraite-(NH4) is optically biaxial (-) with α = 1.490(5), β = 1.540(5) and γ = 1.541(5) (white light); 2Vcalc = 15.7°; and orientation X = b. Electron microprobe analysis gave the empirical formula [(NH4)1.48K0.52]Σ2.00Na0.96(Al0.96Fe3+0.03)Σ0.99(C 2O4)[PO2.97(OH)1.03]2(H2O)2, with the C, N and H contents constrained by the crystal structure. Dendoraite-(NH4) is monoclinic, P21/n, with a = 10.695(6), b = 6.285(4), c = 19.227(12) Å, β = 90.933(10)°, V = 1292(2) Å3, and Z = 4. The structural unit in the crystal structure of dendoraite-(NH4) (R1 = 0.0467 for 1322 Io > 2σI reflections) is a double-strand chain of corner-sharing AlO6 octahedra and PO3OH tetrahedra decorated by additional PO3OH tetrahedra and C2O4 groups. Topologically, this is the same chain found in the structure of thebaite-(NH4). The decorated chains connect to one another through links to NaO7(H2O) polyhedra to form a [Na(H2O)Al(C2O4)(PO3OH)2]2- sheet, which connect to one another through bonds to (NH4)/K and through hydrogen bonds.