Andalusite Photos     
Cochise College               
Photos of Minerals
Geology Home Page

Roger Weller, geology instructor    copyright 2010-R.Weller

andalusite-variety chiastolite-1  
Andalusite is (AlF)2SiO4

One variety of andalusite, chiastolite, forms as gray, block-like crystals that are so
rounded that you are not even sure that what you have is really a crystal.  However,
when slices are made at right angles to the length of the crystal, these slices display
a dark cross or square pattern due to carbonaceous inclusions.  To make matters
even more interesting, each slice in the same crystal will display a slightly different

andalusite-chiastolite                                                                                                                         1
Photo is copyright free only for non-commercial educational uses.
Just credit photo to R.Weller/Cochise College.