A common mineral in igneous
and metamorphic rocks, consisting of
potassium aluminum silicate (KAlSi2O8).
It occurs in the form of vitreous crystals in the monoclinic system, of
various colors, notably white and pink. Orthoclase is one of the end-members
(pure compounds) of the feldspar group.
Hardness 6–6.5, relative density 2.5–2.6.
See also microcline.
AND PLANETARY SCIENCE