Mica is a monoclinic mineral containing a octahedral complex aluminum layer
sandwitched in two tetrahedral SiO-layers.
Crystals are combined by kalium ions under coordinate bonding and piled
up in many layers. Mica can be easily split
into due to a weak bonding force of kalium ions. A minimum unit layer is composed of crystals with sandwitched
structure and kalium ions at either one side and its thickness approximately
1nm (1nm=1 nanometer) .
Muscovite is dioctahedral mica, the number of octahedral layers is two
and the cation is Al. For philogobite, it is
trioctahedral mica, the number of octahedral layers is three and the cation
is Mg and it has a structure in which the
octahedral layer is densely planarized. But for muscovite, one-third of
the octahedral position is empty.
Same as mica, there are kaolin, talc and montmorillonite which also belong
to phylosilicate. Except for montmorilonite
'swelling phillosilicate), mica has one of the highest aspect ratio (major axis / thickness ratio) in non-swelling phillosilicate.
Therefore, mica has a great effect with its shape among the inorganic flake-like
powder materials. |
