How it looks like depends on the original rock and the
temperature at whch it was formed. It forms at very high temperatures
and low pressures.
By .RGB. via Flickr.com
It is usually hard, dense, fine-grained,
homogenous, not foliated, but may be banded.
It has a concoidal,
flintlike fracture, which gives it the broken, horn-like endges.
By Ian Geoffrey Stimpson via
Flickr.com
The
very fine-grained matrix can contain porphyroblasts or poikiloblasts.
It is usually black, grey or bluish in colour.
It often contains
minerals such as micas,
garnets,
sillimanite, pyroxene, cordierite,
andalusite and others.
This site uses British
English, which is the English we use in
Australia.
Disclaimer:
Although
best efforts have been made to ensure that
all the information on this
site is correct,
collecting-rocks-and-minerals.com is not to be blamed should there be a
mistake.
Copyright notice:
All contents of this website are strictly protected
by the Law of
Copyright. What does that
mean?
Copyright
2010-2021
collecting-rocks-and-minerals.com. ALL RIGHTS
RESERVED.