Textures

http://photovalet.com/data/comps/TOP/TOPV03P10_13.jpg

http://www.neublack.com/wp-content/uploads/2008/07/alan-jaras-1.jpg

Oil shale 

http://www.thedailygreen.com/cm/thedailygreen/images/au/tar-sands-md.jpg

http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/SpentShale.jpg/220px-SpentShale.jpg

http://www.groundtruthtrekking.org/static/uploads/photos/natural-oil-seep_2.700x700.jpg

http://www.elsmerecanyon.com/dewittcanyon/oil/d03.jpg