Some rock fragments found in breccias are pieces of more ancient breccias.
Repeated impacts have smashed the older rock and re-fused it with more recently formed breccia. As many as four generations of breccia have been found in a single lunar rock. A common feature of many lunar crystalline rocks is the grinding and crushing, or granulation , of their minerals caused by repeated meteoric bombardment. This makes the original textures difficult to recognize. A glassy material produced by the shock of a meteoric impact coats this rock fragment from an Apollo 11 breccia sample.