Felsite(redirected from Felstone)
Also found in: Dictionary, Wikipedia.
a fine-grained acid extrusive rock consisting of potassic feldspar (orthoclase) and quartz. Felsite sometimes contains acid plagioclase and dark minerals, such as pyroxene and biotite. It results from the recrystallization of volcanic glass during diagenesis and the initial phase of metamorphism. Felsitic texture is characteristic of paleotypical rocks such as quartz porphyries, keratophyres, and orthoclase porphyries. The term “felsite” is sometimes emphasized in the name of a rock, for example, felsodacite and felsophyre.