I collected this rock in 2008 in the Scottish Highlands where the Old Red Sandstone is cut and displaced by the Highland Boundary fault. I was on a field trip led by Midland Valley Exploration, Ltd. I like the fact that this pebble is a miniature thumbnail of the kind of faulting that can deform regions. Besides, how often can you carry a graben around with you in your pocket?
Age & Formation
from the Old Red Sandstone, Devonian age, ~380 Ma.