graywacke

noun

1. (alt-of, alternative, countable, uncountable)Alternative form of greywacke.

   “Hundreds of projectile points and ceramic pieces from the island are stored in the State Museum in Albany, and archaeologists found human bones at a burial site from the early Woodland period at the back of the rock shelter, a 45-foot-long overhang of graywacke, a local sandstone.”