nummulite limestone

Nummulite limestone is a type of sedimentary rock primarily composed of the fossilized remains of nummulites. Nummulites were single-celled marine organisms that were abundant during the Paleogene and Neogene periods, particularly the Eocene Epoch, which spanned from 55.8 to 33.9 million years ago. These organisms were relatively large and had a distinctive lens shape, resembling coins, which is reflected in their genus name, derived from the Latin word for "small coin".12

This limestone formation is widely distributed across Europe, Asia, and northern Africa. The presence of numerous nummulite fossils within the rock makes it a significant indicator for geological dating and correlation of rock strata. The Eocene Epoch, when nummulites thrived, is known for high sea levels that created extensive limestone deposits, such as those found in Egypt that were used to build the pyramids.213