Felsite is fine grained but not glassy, and it may or may not have phenocrysts (large mineral grains). It is high in silica or felsic
, typically consisting of the minerals quartz
, plagioclase feldspar
and alkali feldspar
. Felsite is usually called the extrusive equivalent of granite
A common felsitic rock is rhyolite, which typically has phenocrysts and signs of having flowed. Felsite should not be confused with tuff, a rock made up of compacted volcanic ash that can also be light colored.
For photos of related rocks, see the extrusive volcanic rocks gallery.