What is dacite in geology ?

Dacite : definition

Streckeisen diagrams (or QAPF diagrams) - Classification of plutonic and volcanic rocks
Dacite is a volcanic rock, light gray in color, microlitic in texture with quartz phenocrysts, sodium plagioclase (oligoclase or andesine), and often small amounts of biotite, hornblende and/or pyroxene (augite, hypersthene, enstatite). The dacites give viscous lavas which obstruct the volcanic craters and can cause very violent eruptions (called Plinian) with the emission of pyroclastic clouds, like that of Mount Pelée in 1902 (Martinique). The plutonic equivalent of dacite is quartz diorite (or granodiorite).