Road Aggregate 101: Important Stuff ... 10/11/2012 2 Road Aggregate 101: Source or Geologic Origin TYPICAL ROAD AGGREGATE MATERIALS IN PA •Limestone •Sandstone •Bankrun Gravel (Pit Run) •Shale (mudrock) Limestone Sandstone Bankrun gravel ... Aggregate – a mixture of specific types and sizes of crushed rock or gravel. Generally used