Gneiss rock is easy to
It is a high-grade
regional metamorphic rock with distinctive bands of minerals with
different colours and sizes.
These rocks are folded
the folds can sometimes be too large to see in a rock.
Like many metamorphic
and not "schisty" - they do not break along layers as schists
and some other
main minerals are quartz
Others include mica,
hornblende and staurolite.
Rubem Porto Jr via Flickr.com
Depending the mineralogy these rocks may have
different colours such as gray, pink or others.
Richard Droker via Flickr.com
They often also have
different names such as folded, biotite, or augen gneiss, depending on
their texture or minerals.
sparty lea via Flickr.com
They are medium to coarse grained.
By Mike Beauregard via Flickr.com
are formed at very high temperatures and pressures from rock such as
siltstone, mudstone, shale and granitoids. They are used in building