The feldspar mineral
group is one of the most important and largest groups of silicate
It can be further
divided into three mineral groups.
These are alkali, plagioclase, and potassium, aka K-feldspar.
By ZEISS Microscopy via Flickr.com
is the largest group of feldspars. It consists of a solid solution of
minerals with compositions of those between albite and anorthite.
To name a few - oligoclase is closest to albite, andesine is close to
albite, labradorite is closer to anothite, and bytownite is closest to
Geoffrey Stimpson via Flickr.com
Another group is alkali
feldspars - this group contains a solid solution
which starts with the composition of albite (which is
consequently both plagioclase and alkali feldspar), and ends with the
composition of orthoclase.
thomasina via Flickr.com
is a group that
doesn't contain a solid solution but is rather a polymorphic group (all
the minerals in the group have the same chemical formula). It does
start with orthoclase
(which is consequently both Alkali and K-feldspar); other
minerals are sanidine and microcline.