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

Abstract

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 colourless blades up to ~0.1 mm in length. The streak is white and lustre is vitreous, Mohs hardness is 2½, 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(C2O4)[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.

Minerals, crystal structures and geochemistry

“…The first article in this special issue devoted to Pete, 'Reaphookhillite, MgZn 2 (PO 4 ) 2 ⋅4H 2 O, the Mg analogue of parahopeite from Reaphook Hill, South Australia' by Peter Elliott describes a new phosphate mineral from a mine famous for unusual mineral associations, described and studied in the past by Pete Williams. This article presents a picture of a thin tabular crystal of colourless and transparent reaphookhillite (0.3 mm wide) formed as an overgrowth on a parahopeite crystal (Elliot, 2022) and list the minerals associated with them (Kampf et al, 2022a(Kampf et al, , 2022b. Both articles present images of sprays of each mineral.…”

“…This article presents a picture of a thin tabular crystal of colourless and transparent reaphookhillite (0.3 mm wide) formed as an overgrowth on a parahopeite crystal (Elliot, 2022). Papers by Anthony R. Kampf, Mark A. Cooper, Aaron J. Celestian, Chi Ma and Joe Marty ‘Dendoraite-(NH 4 ), a new phosphate–oxalate mineral related to thebaite-(NH 4 ) from the Rowley mine, Arizona, USA' and ‘Relianceite-(K), a new phosphate–oxalate mineral related to davidbrownite-(NH 4 ) from the Rowley mine, Arizona, USA' also describe new phosphate mineral species [dendoraite-(NH 4 ), (NH 4 ) 2 NaAl(C 2 O 4 )(PO 3 OH) 2 (H 2 O) 2 and relianceite-(K), K 4 Mg(V 4+ O) 2 (C 2 O 4 )(PO 3 OH) 4 (H 2 O) 10 ] and list the minerals associated with them (Kampf et al ., 2022a, 2022b). Both articles present images of sprays of each mineral.…”

Relianceite-(K), a new phosphate–oxalate mineral related to davidbrownite-(NH4) from the Rowley mine, Arizona, USA

“…The new mineral was found in a hot and humid area of the mine (see figure 26 in Wilson, 2020) in an unusual bat guano-related, post-mining assemblage of phases that include a variety of vanadates, phosphates, oxalates and chlorides, some containing NH 4 + . This secondary mineral assemblage is found growing on baryte–quartz-rich matrix and, besides relianceite-(K), includes allantoin (Kampf et al , 2021c), ammineite, antipinite, aphthitalite, bassanite, biphosphammite, cerussite, davidbrownite-(NH 4 ) (Kampf et al , 2019a), dendoraite-(NH 4 ) (Kampf et al , 2022), fluorite, halite, hydroglauberite, mimetite, mottramite, natrosulfatourea (Kampf et al , 2021c), perite, phoxite (Kampf et al , 2019b), rowleyite (Kampf et al , 2017), salammoniac, struvite, thebaite-(NH 4 ) (Kampf et al , 2021a), thénardite, urea, vanadinite, weddellite, willemite, wulfenite, and several other potentially new minerals. Relianceite-(K) was found in intimate association with antipinite, dendoraite-(NH 4 ), fluorite, mimetite, mottramite, rowleyite, salammoniac, struvite, vanadinite, willemite, wulfenite, and at least one other potentially new species.…”

“…Including the new mineral described herein, relianceite-(K), eight new minerals have now been described from this assemblage. Relianceite-(K), K 4 Mg(V 4+ O) 2 (C 2 O 4 )(PO 3 OH) 4 (H 2 O) 10 , is one of only five minerals known to include both phosphate and oxalate group, the others being davidbrownite-(NH 4 ), (NH 4 ,K) 5 (V 4+ O) 2 (C 2 O 4 )[PO 2.75 (OH) 1.25 ] 4 ⋅3H 2 O (Kampf et al , 2019a), dendoraite-(NH 4 ), (NH 4 ) 2 NaAl(C 2 O 4 )(PO 3 OH) 2 (H 2 O) 2 (Kampf et al , 2022), phoxite, (NH 4 ) 2 Mg 2 (C 2 O 4 )(PO 3 OH) 2 (H 2 O) 4 (Kampf et al , 2019b), and thebaite-(NH 4 ), (NH 4 ,K) 3 Al(C 2 O 4 )(PO 3 OH) 2 (H 2 O) (Kampf et al , 2021a); all of these, except phoxite, are known only from the Rowley mine bat guano assemblage. One of these, dendoraite-(NH 4 ), is intimately associated with relianceite-(K) and is described in a companion paper (Kampf et al ., 2022).…”