Distinctive features:  
Colour and texture. Often flow-banded and porphyritic and plagioclase phenocrysts occur as thin laths. Biotite, hornblende and pyroxenes may be seen with the aid of a hand lens, but they can be difficult to identitfy because they are small.

Colour: 
White to black, but mostly medium grey.

Texture and granularity: 
Aphanitic to finely granular, porphyritic and flow-banded.

Composition: 
Fine-grained ground mass of plagioclase, with smaller amounts of hornblende, biotite and augite, which may occur as small phenocrysts.

Field associations: 
Lava flows and small intrusions associated with volcanic mountain ranges.

Varieties:
Hornblende augite andesite, which is andesite with phenocrysts of hornblende and augite.

 

Abundant in continental collison zones, such as the Andes, Cascades, Carpathians, Indonesida, Japan and other western Pacific volcanic islands.

 

Roadstone aggregate.