Cortex (archaeology)

In lithic analysis in archaeology the cortex is the outer layer of rock formed on the exterior of raw materials by chemical and mechanical weathering processes. It is often recorded on the dorsal surface of flakes using a three class system: primary (100% cortex), secondary (100%>x>0%), and tertiary (0%). The amount of cortex present on artifacts in an archaeological assemblage may indicate the extent of lithic reduction that has occurred.