Cutting

Stone is originally formed in boulders ranging in weight between 20 and several hundred pounds.  Normally you won't find small single stones under 10-15 lbs.; therefore smaller sizes are cut from larger boulders.  Boulders are first cut into slabs and then cut into smaller pieces that can be easily handled. The cut pieces are usually flat on at least two and even three sides and will always be irregular in shape. 

Stone Hardness

Stone for carving is gauged in four hardnesses: soft, medium, hard and extreme.  Soapstone (talc block) is considered the softest.  Alabaster (a gypsum base stone) is medium hard along with limestone and sandstone. Marble is considered hard; granite is the extreme.