Nummulite

A nummulite is a large lenticularfossil, characterised by its numerous coils, subdivided by septa into chambers. They are the shells of the fossil and present-day marine protozoanNummulites, a type of foraminiferan. Nummulites commonly vary in diameter from 13 to 50 mm (0.51 to 1.97 in) and are common in Eocene to Miocene marine rocks, particularly around southwest Asia and the in the area that once constituted the Tethys Ocean, such as Eocene limestones from Egypt or from Pakistan. Fossils up to six inches wide are found in the Middle Eocene rocks of Turkey. They are valuable as index fossils.

The ancient Egyptians used nummulite shells as coins and the pyramids were constructed using limestone that contained nummulites. The name Nummulites is a diminutive form of the Latinnummulus 'little coin', a reference to their shape.

In 1913, naturalist Randolph Kirkpatrick published a book, The Nummulosphere: an account of the Organic Origin of so-called Igneous Rocks and Abyssal Red Clays, proposing the unconventional theory that all rocks had been produced through the accumulation of forams such as Nummulites.