nature of catapult stone

[richsc]

I was just speaking with a hopefully new member to Legio XX, Sean Kuhl (acquainted with you Sander.he says hello). He was relating experiences with European reenactors (are there really hundreds of naked Belgian/Gaulish warrior reenactors????) and he was relating how large artillery stones were known to explode or fragment on impact. I happened to remember all the stone shot at Pompeii, from Sulla's seige around 90BC, if I remember right, which is all solid and unbroken. Some had left impressions in the town walls.<br>
Stone of course can be many different types: sandstone and shale would be more likely I would think to break up and fragment than granite. Explode?<br>
Any references out there to the types of projectiles used in roman artillery? <p></p><i></i>