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

Kampf, Anthony R. and Cooper, Mark A. and Celestian, Aaron J. and Ma, Chi and Marty, Joe (2022) Dendoraite-(NH₄), a new phosphate-oxalate mineral related to thebaite-(NH₄) from the Rowley mine, Arizona, USA. Mineralogical Magazine, 86 (4). pp. 531-538. ISSN 0026-461X. doi:10.1180/mgm.2021.98.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Article
Kampf, Anthony R.0000-0001-8084-2563
Celestian, Aaron J.0000-0003-0775-6380
Ma, Chi0000-0002-1828-7033
Additional Information:Anonymous reviewers and Pete Leverett are thanked for constructive comments, which improved the manuscript. Keith Wentz, claim holder of the Rowley mine, is thanked for allowing underground access for the study of the occurrence and the collecting of specimens, along with Frank Hawthorne for providing access to the single-crystal instrument at the University of Manitoba. This study was funded, in part, by the John Jago Trelawney Endowment to the Mineral Sciences Department of the Natural History Museum of Los Angeles County.
Issue or Number:4
Record Number:CaltechAUTHORS:20220829-467858200
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116622
Deposited By: Donna Wrublewski
Deposited On:22 Sep 2022 19:25
Last Modified:22 Sep 2022 19:25

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