TY - JOUR
T1 - Crystal chemistry of neptunite from the Khan Bogdo alkaline massif (Mongolia)
AU - Zolotarev, A. A.
AU - Vladykin, N. V.
AU - Krivovichev, S. V.
AU - Panikorovskii, T. L.
PY - 2016/1/1
Y1 - 2016/1/1
N2 -
Crystal chemical characteristics have been studied for neptunite from alkaline granites of the Khan Bogdo massif (Southern Mongolia). The mineral occurs to be the practically clear Fe-variety of its species. Refinement of its crystal structure was carried out in two space groups: centric C2/c and acentric Cc. It is indicated that correct space group is the acentric Cc due to ordering of octahedral cations Ti and Fe. The structure was refined to R
1
= 0.025 (wR
2
= 0.057) for 4889 reflections with |Fo| ≥ 4σF. Unit cell parameters: a = 16.4542(7), b = 12.5115(4), c = 9.9980(4) Å, β = 115.542(5)°, V = 1857.10(15) Å
3
, Z = 4. Ti octahedra show strong distortions: one bond Ti-O 1.75 Å, another bond 2.20 Å, and four Ti-O bonds around 2.0 Å. Fe octahedra have a more regular shape with an average bond length Fe-O 2.13-2.14 Å. Empirical formula calculated on the basis of chemical analysis is (K
0.86
Cs
0.02
Zn
0.02
Ca
0.01
)
S0.91
Na
1.90
Li
0.82
(Fe
1.54
2+
Fe
0.22
3+
Mn
0.16
Mn
0.04
)
S1.96
Ti
2.1
(Si
7.76
Al
0.25
)O
24
. Structural formula is K
0.97
Na
1.90
(Li
0.94
Na
0.06
)
S1.00
(Fe
1.80
Mn
0.15
Mg
0.05
)
S2.00
Ti
2
Si
8
O
22
(O,OH)
2
. Idealized formula is KNa
2
LiFe
2
Ti
2
Si
8
O
24
AB -
Crystal chemical characteristics have been studied for neptunite from alkaline granites of the Khan Bogdo massif (Southern Mongolia). The mineral occurs to be the practically clear Fe-variety of its species. Refinement of its crystal structure was carried out in two space groups: centric C2/c and acentric Cc. It is indicated that correct space group is the acentric Cc due to ordering of octahedral cations Ti and Fe. The structure was refined to R
1
= 0.025 (wR
2
= 0.057) for 4889 reflections with |Fo| ≥ 4σF. Unit cell parameters: a = 16.4542(7), b = 12.5115(4), c = 9.9980(4) Å, β = 115.542(5)°, V = 1857.10(15) Å
3
, Z = 4. Ti octahedra show strong distortions: one bond Ti-O 1.75 Å, another bond 2.20 Å, and four Ti-O bonds around 2.0 Å. Fe octahedra have a more regular shape with an average bond length Fe-O 2.13-2.14 Å. Empirical formula calculated on the basis of chemical analysis is (K
0.86
Cs
0.02
Zn
0.02
Ca
0.01
)
S0.91
Na
1.90
Li
0.82
(Fe
1.54
2+
Fe
0.22
3+
Mn
0.16
Mn
0.04
)
S1.96
Ti
2.1
(Si
7.76
Al
0.25
)O
24
. Structural formula is K
0.97
Na
1.90
(Li
0.94
Na
0.06
)
S1.00
(Fe
1.80
Mn
0.15
Mg
0.05
)
S2.00
Ti
2
Si
8
O
22
(O,OH)
2
. Idealized formula is KNa
2
LiFe
2
Ti
2
Si
8
O
24
KW - Equivalent and anisotropic displacement parameters
KW - Fe-dominant neptunite
KW - Inter-atomic distances
KW - Mangan-neptunite
KW - Pyroxene type and octahedral chains
KW - Refined crystal structure
UR - http://www.scopus.com/inward/record.url?scp=85063737832&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:85063737832
VL - 145
SP - 112
EP - 127
JO - ЗАПИСКИ РОССИЙСКОГО МИНЕРАЛОГИЧЕСКОГО ОБЩЕСТВА
JF - ЗАПИСКИ РОССИЙСКОГО МИНЕРАЛОГИЧЕСКОГО ОБЩЕСТВА
SN - 0869-6055
IS - 2
ER -