Biltmore is a tumbled castle rock style natural thin stone veneer.  The thin veneer starts as natural sandstone sheets quarried in the USA.  The sheets or slabs of stone are fed into a hydraulic press where a craftsman splits them into usable rectangular blocks.  The blocks of stone are fed into a tumbler; the tumbler somewhat resembles and works like a large cement mixer. As the pieces of stone tumble and bash into each other, the sharp edges are worn off. This process gives the stone a much more worn, softer, and older appearance.  The outer faces of the tumbled blocks are sawn off to create the thin stone veneer and finish Biltmore.