Non-porous type of marble resulting from deposition by springs or rivers. It is often beautifully colored and banded as a result of the presence of iron compounds or other impurities. When used for decorative purposes, it is also known as onyx marble. Marble is a non-foliated metamorphic rock compressed mostly of calcite, a crystalline form of calcium carbonate. It is formed from carbonate rocks and limestone. Cut all sides to full-dimension with a tumbled surface; Consistent thickness of 1". Often used for patios and pathways.