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Thebaite-(NH 4 ), (NH 4 ,K) 3 Al(C 2 O 4 )(PO 3 OH) 2 (H 2 O), a new phosphate–oxalate mineral from the Rowley mine, Arizona, USA
Thebaite-(NH 4 ), (NH 4 ,K) 3 Al(C 2 O 4 )(PO 3 OH) 2 (H 2 O), is a new mineral species (IMA2020-072) 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 chlorid...
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| Published in: | Mineralogical magazine 2021-06, Vol.85 (3), p.379-386 |
|---|---|
| Main Authors: | , , , , |
| Format: | Article |
| Language: | English |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | Thebaite-(NH
4
), (NH
4
,K)
3
Al(C
2
O
4
)(PO
3
OH)
2
(H
2
O), is a new mineral species (IMA2020-072) 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 NH
4
+
. Other secondary minerals found in association with thebaite-(NH
4
) are antipinite, vanadinite and at least one other new mineral. Crystals of thebaite-(NH
4
) are colourless blades up to ~0.1 mm in length. The streak is white, lustre is vitreous, Mohs hardness is 1½–2, tenacity is brittle and fracture is splintery. There are two good cleavages in the [010] zone, probably {100} and {10
$\bar{2}$
}. The calculated density is 2.093 g⋅cm
–3
. Thebaite-(NH
4
) is optically biaxial (–) with α = 1.490(2), β = 1.534(2), γ = 1.570(2) (white light); 2V = 82.7(5)°; slight
r
>
v
dispersion; and orientation
X
=
b
,
Y
^
c
= 13° in obtuse β. Electron microprobe analysis gave the empirical formula [(NH
4
)
2.12
K
0.69
Na
0.20
]
Σ3.01
(Al
0.84
Fe
3+
0.11
V
3+
0.04
)
Σ0.99
(C
2
O
4
)[(P
0.98
Si
0.02
)O
3
OH]
2
(H
2
O), with the C, N and H contents constrained by the crystal structure. Raman spectroscopy confirmed the presence of NH
4
and C
2
O
4
. Thebaite-(NH
4
) is monoclinic,
P
2
1
/
c
, with
a
= 11.156(9),
b
= 6.234(6),
c
= 18.651(16) Å, β = 102.928(15)°,
V
= 1264.2(19) Å
3
and
Z
= 4. The structural unit in the crystal structure of thebaite-(NH
4
) (
R
1
= 0.0612 for 863
I
o
> 2σ
I
reflections) is a double-strand chain of corner-sharing AlO
6
octahedra and PO
3
OH tetrahedra decorated by additional PO
3
OH tetrahedra and C
2
O
4
groups. The decorated chains connect to one another through bonds to NH
4
+
and K
+
and through hydrogen bonds. |
|---|---|
| ISSN: | 0026-461X 1471-8022 |
| DOI: | 10.1180/mgm.2021.26 |