Riven or Honed Slate
Lower absorbency slate is a very dense compact material and tends to have a fairly smooth regular surface. Common examples include slates from Brazil, China, Wales and Portugal which normally have a natural riven surface, but are sometimes mechanically honed to make them smooth. Higher absorbency slate is far less dense; a softer, friable and more absorbent material. The surface of higher absorbency slate tends to be more laminated and irregular. Common examples include slates from India and Cornwall. Porosity Test: Lower absorbency - up to 1 hour; Higher absorbency - up to 15 minutes.