Intermediate rocks are another large group of igneous rocks. The rocks contain 53–66% SiO2. The main mineral is feldspar, often with a small amount of quartz. Intermediate rocks contain more dark minerals, such as hornblende and pyroxene (usually approximately 30%), than acidic rocks. Common intrusive intermediate rocks include diorite and quartz diorite, and common extrusive intermediate rocks include andesite and dacite.