Maybe something that would get peoples attention
I believe the answer is Capillaries
Slate starts out as shale under the surface of the Earth before its metamorphosis. It is typically gray in color and splits along long flat planes. It is also does not allow water or other liquids to pass through it. Slate is most often used as a roofing material, decorative gardening stone and a base for snooker tables. In the Victorian era, it was commonly used as a writing board.
Marble is another one of the metamorphic rocks and is a metamorphosed limestone. It has a hard crystalline rock appearance and was the stone of choice in ancient Greece. In fact, more than 22,000 tonnes of marble were used to build the ancient Greek Parthenon and marble remains a popular building and sculpture material today. It can also be ground down to make cleaning products or soaps.
Schist is another metamorphic rock that is formed from either mud or shale. However, it is formed at a much higher temperature than slate is. Schist is a fairly weak rock so it does not make for a good building material. It is used for paving and occasionally sculpture.
