[Terra]

If it's white and it made of little beads than that is not the favorite styro for props (which we call the blue or pink foam). But is completely doable to make tombstones. I hear it's a little tougher to get the details (not sure, never used it). I noticed that you live in SC. In southern climes the hardware stores don't readily carry the blue or pink foam so you may have a tougher time finding it.

Here's a picture of tombstones being made with blue:

and pink foam: