A type of bitumin (semisolid to solid hydrocarbon substance) which is composed mostly of alkanes (or paraffins) with high molecular weights. The substance is a waxy solid found in irregular veinlike deposits within stressed rocks and have colors ranging from greenish to brown to jet black. It is formed from oils, or liquid petroleum, of the same composition which have been exposed to the surface, have been exposed to oxidation and biodegradation, and/or whose liquid components have evaporated.