We sell stones that are safe to carve. Generally these fall into three categories: alabaster, limestone and marble. These are all calcium based. Alabaster is the softest of these (2 to 2.5 hardness) composed of gypsum or chemically, calcium sulphate. It can be carved with wood carving chisels and rasps, although stone chisels are faster. They should be sanded to at least 600 grit to get a shine and they make beautiful colorful indoor sculptures.
Limestone is composed of calcium carbonate (old bones) that got cemented into a sedimentary stone. It is a little bit harder (2.5 to 3 hardness) but still easy to carve although there is great variability in limestone hardness. There are many colors of limestone from gray to tan to yellow to white. Limestone can be polished but does not achieve the crystalline finish of alabaster or marble. It can be left outdoors.
Marble is limestone that has been heated and compressed – metamorphosed – into that crystalline carving stone. Its hardness varies quite a bit (3 to 4.5) with some of those in the Southwest U.S. being very hard (5). Like alabaster, marbles come in a wide range of colors but can be displayed outdoors. In the marble family are travertines that are formed with holes in them and onyx marbles (as opposed to silicate onyx) that have different carving characteristics.
Please note: These are natural materials. For the most part they are not like dimensional lumber where exact sizes can be specified. We will come as close as we can to your request but there may be imperfections and size variations in the stone.If cutting a stone results in small unsellable pieces, we will ask you to buy the entire original piece before we cut it. Artists are flexible with their media. right?