Muscovite
:''Muscovite can also refer to a native or inhabitant of
Muscovy or
Moscow principality in
Russia.
Muscovite, also known as
potash mica, is a
phyllosilicate mineral of
aluminium and
potassium with formula: KAl
2(AlSi
3O
10)(F,OH)
2. It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets), which are often highly elastic. Muscovite melts at approximately 1320°C, has a
Mohs hardness of 2 - 2.25 and a
specific gravity of 2.76 - 3. It can be colorless or tinted through
grays,
browns,
greens,
yellows, or (rarely)
violet or
red, and can be transparent or translucent. The green
chromium rich variety is called
fuchsite.
Muscovite is the most common mica, found in
granites,
pegmatites,
gneisses and
schists, and as a contact
metamorphic rock or as a secondary
mineral resulting from the alteration of
topaz,
feldspar,
kyanite, etc. In pegmatites, it is often found in immense sheets that are commercially valuable. Muscovite is in demand for the manufacture of
fireproofing and insulating materials and to some extent as a
lubricant.
The name of muscovite comes from Muscovy-glass, a name formerly used for the mineral because of its use in
Russia for
windows.Muscovite is
anisotropic, and has quite a high
birefringence.Its crystal system is
monoclinic.
*
List of minerals* http://www.micronized.com/mica.htm
