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KFeldspat

KFeldspat, or potassium feldspar, is a group of rock-forming tectosilicate minerals in which potassium is the dominant alkali cation. The principal minerals in this group are orthoclase, microcline, and sanidine, all with the ideal formula KAlSi3O8. Alkali feldspars form a solid solution series with sodium feldspar (albite, NaAlSi3O8) and occur widely in felsic igneous rocks. In terms of crystal structure, orthoclase and sanidine are monoclinic, while microcline is triclinic; all show two good cleavages at or near 90 degrees and a vitreous luster. Color ranges from white and colorless to pink, red, or green, and crystals can be prismatic or tabular.

KFeldspat is a major constituent of granitic rocks, granodiorites, and pegmatites, and also appears in rhyolites

Uses and significance: as a major source of potassium oxide (K2O), potassium feldspar is important in the

Distinction: KFeldspat is part of the alkali feldspar group, distinct from plagioclase feldspars (Na-Ca feldspars).

and
certain
metamorphic
rocks.
It
is
relatively
resistant
to
chemical
weathering
but
alters
over
long
timescales
to
clay
minerals
such
as
illite
and
kaolinite,
contributing
to
soil
formation.
glass
and
ceramic
industries
as
a
flux
and
refining
agent.
It
also
serves
as
a
source
of
potassium
for
agricultural
fertilizers
and
is
used
in
radiometric
dating
(K-Ar
and
Ar-Ar).