Geoscience Reference
In-Depth Information
Mixed ortho- and triorthogroups [SiO
4
] and [Si
3
O
10
] exist simultaneously in
HO
4
[Si
3
O
10
] [SiO
4
]. The triorthogroups have similar consideration of diverse tetra-
hedral anions as in earlier observed Ca
6
[SiO
4
]
[Si
3
O
10
]
[57]
.
Discrete 4-membered ring [Si
4
O
12
] with 2/m symmetry exists in K
4
Sc(OH)
2
[Si
4
O
12
] structure. Likely 4-membered rings with different symmetry were found in
several compounds like Ba
2
FeR
2
Ti
2
O
2
H
2
O
[54]
,Na
3
CaPSiO
7
[58]
,
Ca
2
R
2
[Si
4
O
12
]
[59]
, (Ba,K,Na)
8
(Ti,Nb)
9
(O,OH)
10
[Si
4
O
12
]
4
[Si
4
O
12
]
2
OH
nH
2
O
[60]
,Ba
2
(Fe,
Ti,Mg)
2
(H
2
O)[Si
4
O
12
]
[61]
, KHSiO
3
[62]
,Ba
12
Mn
6
(OH,O)
2
[Si
4
O
12
]Cl
9
(OH,
H
2
O)
7
[63]
, (Na,K)
2
2
x
(Nb,Ti) (O,OH) [Si
2
O
6
]
2H
2
O
[64]
,Ba
4
Ti
4
(Ti,Nb,Fe)
4
ClO
6
[Si
4
O
12
]
[65]
.
Figure 7.8 Triorthosilicates,
Y
3
[Si
3
O
10
], and K
3
Y[Si
3
O
8
]
(OH)
2
[53]
.
Figure 7.9 Structure of Na
5
Ce[Si
4
O
12
]
[66]
.
