breccia

Angular chips re-cemented into one stone: the anti-conglomerate. Every fragment keeps its corners, because nothing got tumbled round before the rock healed back together. Round pebbles means conglomerate; sharp shards means breccia.

The chips are often all one rock, broken in place and glued back together, where conglomerate gathers pebbles of everything. A collapse breccia like the Mackinac one mixes several, so angularity is the test that always holds and the sorting is not. The famous one here is the Mackinac Breccia at the Straits: Silurian and Devonian rock that collapsed into the holes left when groundwater dissolved the salt beds underneath it, then healed back together. Look at St. Ignace, Mackinac Island and Bois Blanc.