Distinctive features:  
Fine-grained to aphanitic, buff to dark brown compact rock with paralle streaks or lenticles of black gass.

Colour: 
Pale cream to brownish to dark red-brown.

Texture and granularity: 
Fine-grained to aphanitic and flow foliation is often present.

Composition: 
Usually trachytic/phonolitic to andesitic.

Field associations: 
Exclusively produced by violently explosive volcanoes.

Varieties:
Sillar, which is poorly consolidated rock of same origin as ignimbrite but in which pumice blocks have not collapsed to form plates of black glass and which is poorly sorted.

 

Worldwide -- asociated with andesitic to phonolitic/trachytic volcanoes.

 

Local building construction, aggregate.