The next suite of rocks are called the intermediates and are the extrusive rocks andesite and dacite and the intrusive rocks diorite and granodiorite . These rocks are composed of plagioclase - a calcium rich feldspar, amphibole, and some pyroxene and quartz. Andesite often has a porphyritic texture. Andesite is named after the Andes where it is found in great abundance occurring along convergent plate margins. Diorite, the intrusive equivalent, generally has well-developed crystals.
Pegmatites are extremely coarse-grained felsic rocks.
These rocks can have crystals several feet across.