Distinctive features:  
Coarse-grained, pale-coloured gneissose rock, containing abundant feldspar.

Colour: 
Whitish to dark grey -- the darker varieties containing more biotite.

Texture and granularity: 
Gneissose, coarse-grained.

Composition:
Mostly feldpsar, with quartz, mica, hornblende and garnet.

Field associations: 
In roots of eroded fold mountain systems.

Varieties:
Depends on the source rock. Granitic gneiss is the most common, but basic varieties also occur.

 

Worldwide, but always in roots of fold mountain systems.

 

Construction, ornamental, aggregate.