Chemistry Reference
In-Depth Information
Li
Polylithionite
K Al
IV
Li
2
Si
3
Al
IV
O
10
(OH,F)
2
Trilithionite
K Al
IV
Li
1,5
Si
3
Al
IV
O
10
(OH,F)
2
1,5
Zinnwaldite
K Al
IV
LI Fe Si
3
Al
IV
O
10
(OH,F)
2
Protolithionite
K Al
IV
Li
0,6
Fe
0,6
Si
3
Al
IV
O
10
(OH,F)
2
1,4
miscibility gap
Al
IV
M
2+
(Fe, Mg)
Muscovite
K Al
IV
Si
3
Al
IV
O
10
(OH)
2
2
Annite - Phlogopite
Biotite
Siderophyllite - Eastonite
K (Fe, Mg)
3
Si
3
Al
IV
O
10
(OH,F)
2
K Al
IV
(Fe, Mg) Si
3
Al
IV
O
10
(OH)
2
2
Figure 3.15
Lithium-bearing micas.
Margarite occurs mainly in emery deposits (metamorphosed bauxites)
with corundum, diaspore. Also appears in iron-poor (calcic) peraluminous
schists with kyanite, or andalusite. The sample featured on the CD from
Ovala (Gabon), is a rock of metasomatic origin, where margarite is associ-
ated with kyanite and anorthite (Demange, 1976).
Clintonite and xanthophyllite are minerals from calcic and magnesian
schists where they are associated with chlorite, from metamorphic dolos-
tones and skarns.
3.2.1.8 Stilpnomelane
Stilpnomelane is a phyllosilicate with a structure similar to that of micas:
with sheets made of two tetrahedral layers separated by an octahedral
layer:
the octahedral layer is complete,
the tetrahedral layers are incomplete and are formed by regularly dis-
posed “islands” of 7 rings of (SiO
4
)
4−
tetrahedra,
the interlayer (K, with small amounts of Na and Ca) is incomplete.
