Chemistry Reference
In-Depth Information
unit cell
[Si
4
O
10
]
4−
OH
(001) plane
2K
4 Si, Al
6 Mg
6 O
2 O, 2 (OH)
2 O, 2 (OH)
4 Si, Al
2K
6 O
4 Si, Al
Figure 3.11
Structure of the micas.
defines the octahedral sites Y on the intermediate octahedral layer. The
filling of the octahedral sites can be 4 Y (dioctahedral mica) or 6 Y cati-
ons (trioctahedral micas). The sheets are bound to each other through
an interlayer, made of large ions in 12-fold coordination (X site). Ani-
ons (OH, F, Cl) are placed at the center of the hexagons of tetrahedral
layers. Thus the general formula for mica is:
