The Origin of Fossilized Stones
Stone Rissani is famous for the fossils contained within it from the Primary Era. It is mined in the Moroccan Sahara near the town of Rissani (from which it derives its name). It is a fossilized marble rock, containing mainly cephalopods, which only appear if the stone is polished. Otherwise the fossil merges with the stone. The rock is very hard; it has a coefficient of zero capillary. The age of the fossils are dated to the Upper Devonian Period (about 360 million years). A majority of the fauna within the rock is made up of goniatites, ammonites, orthoceras, corals, and trilobites. Iron oxide and carbonate deposits give the rock its black color.