15 May 2012
Diabase dike in diabase
Posted by Callan Bentley
Seen in rip-rap on the side of Naked Creek, a week ago yesterday:
This boulder is exotic to its current location. It is typical of medium- and coarser-grained diabase from the Culpeper Basin, a Triassic rift valley east of the Blue Ridge. The main minerals are plagioclase (light-colored) and pyroxene (dark colored).