Marble is a metamorphic rock consisting of Limestone but composed mostly of Calcite. It is used extensively for sculpture, building materials and has many decorative uses. The pure white Marble is probably the most common form known, but the characteristic swirls and veins of many colored Marble varieties are usually due to various mineral impurities such as Clay, Silt, Sand, Iron Oxides or Chert.
Orthoceras is a genus of extinct Nautiloid Cephalopod. These fossils are common and have a global distribution which occur in any marine rock, especially Limestone. These are slender, elongated shells with the middle of the body chamber transversely constricted and a sub-central orthochoanitic siphuncle. The surface is ornamented by a network of fine lirae or fine lines/ridges.