Rhyolite

Rhyolite Samples from NC. Material is very porous and coarse to medium grained. It is earthy in luster. Colors are light grey to cream colored to black. Known source is in Adams County Pennsylvania, and has been found distributed into West Virginia and Ohio. The minerals present are seen as specks in the stone are biotite micas, horneblende and muscovites, among others.

References

DeRegnaucourt, Tony and Georgiady, Jeff, Prehistoric Cherts of the Midwest.