A variety of alkali feldspar consisting of parallel or subparallel intergrowths in which the potassium-rich phase (commonly microcline) appears to be the host from which the sodium-rich phase (commonly albite) exsolved; such exsolved areas may be visible to the naked eye, typically forming strings, lamellae, blebs, films, or irregular veinlets; where texture is invisible to the eye but can be resolved with a microscope, it is microperthite. Compare: antiperthite; cryptoperthite; microperthite.