Dacite

Dacite
Igneous rock
Dacite from the Mt. Bijang lava dome, Laguna Volcanic Field, Philippines.
Composition
ClassificationFelsic
PrimaryPlagioclase feldspar, quartz
SecondaryHornblende, potassium feldspar, biotite, augite, volcanic glass
TextureAphanitic or porphyritic
EquivalentsIntrusive variant is granodiorite if it contains 10% to 35% potassium feldspar or tonalite if it contains less than 10% potassium feldspar relative to the total feldspar content.

Dacite (/ˈdeɪsaɪt/) is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. It is composed predominantly of plagioclase feldspar and quartz.

Dacite is relatively common, occurring in many tectonic settings. It is associated with andesite and rhyolite as part of the subalkaline tholeiitic and calc-alkaline magma series.