OBSIDIAN
Obsidian, a form of volcanic glass, was mined in the local area. Obsidian is very hard and breaks in very sharp edges, making it an excellent choice for arrowpoints and scrappers.  The local obsidian is good quality for tool making and was traded far and wide. 

BASALT
Basalt is also a very hard, dark rock.  It was used mostly for pounding and cutting tools such as hammers and axes.  Like obsidian, basalt is found locally mostly in the southern section of the monument.