The steep road leading to the visiting center at Smith Mountain Dam has been cut out along a massive wall of rock. This rock that covers the surface of the whole mountain is a schistose, metamorphic form called “phyllite.”
Phyllite is unique in that its cleavage surfaces display a silky sheen due to the inclusion of minute crystals of sericite mica and chlorite as seen in the lower photo. Some exposed surfaces of phyllite may be tinted with a reddish iron compound known as hematite or yellowish limonite. White quartzite is often visible between layers of weathered phyllite as seen in the road cut along the rock wall, top photo.
Deep core drill samples on display at the visitor center indicate that the unweathered inner mountain is composed of quartz-chloritoid gneiss.
Copyright © 2001–2002 William T. Hathaway.