traprock
/ˈtræprɑk/
noun
- A dark, fine-grained igneous rock, such as basalt or diabase, used in construction for roads and buildings.
- The driveway was paved with crushed traprock, which is very durable.
- The old stone walls in New England are sometimes made of local traprock.
- Traprock is often quarried for use as railroad ballast.