FELDSPATHS
Noun
feldspaths
plural of feldspath
Source: Wiktionary
FELDSPATH
Feld"spar`, Feld"spath`, n. Etym: [G. feldspath; feld field + spath
spar.] (Min.)
Definition: A name given to a group of minerals, closely related in
crystalline form, and all silicates of alumina with either potash,
soda, lime, or, in one case, baryta. They occur in crystals and
crystalline masses, vitreous in luster, and breaking rather easily in
two directions at right angles to each other, or nearly so. The
colors are usually white or nearly white, flesh-red, bluish, or
greenish.
Note: The group includes the monoclinic (orthoclastic) species
orthoclase or common potash feldspar, and the rare hyalophane or
baryta feldspar; also the triclinic species (called in general
plagioclase) microcline, like orthoclase a potash feldspar; anorthite
or lime feldspar; albite or soda feldspar; also intermediate between
the last two species, labradorite, andesine, oligoclase, containing
both lime and soda in varying amounts. The feldspars are essential
constituents of nearly all crystalline rocks, as granite, gneiss,
mica, slate, most kinds of basalt and trachyte, etc. The
decomposition of feldspar has yielded a large part of the clay of the
soil, also the mineral kaolin, an essential material in the making of
fine pottery. Common feldspar is itself largely used for the same
purpose.
Source: Webster’s Unabridged Dictionary 1913 Edition