Chert breccia, Rincon Mountains, AZ


I collected this rock in ~1972 in the Agua Verde area, which lies on the south flank of the Rincon Mountains.  I like the fact that it hangs together cohesively even though completely smashed.  The brecciation and fracturing must have been accompanied by precipitation of some silica cement. 

Age & Formation
From within the Horquilla Formation of Pennsylvanian age, ~300 Ma.