Nummulitic limestone. Polarised light micrograph of a thin section of a nummulitic limestone found in Allicante, Spain. The large coloured objects are the remains of large foraminifera, Nummulites sp. These are embedded in a fine-grained matrix of calcareous remains of smaller, planktonic organisms. This type of rock is found in South Europe and North Africa, and was deposited during the eocene and oligocene epochs, 37-54 million years BP (before present). Horizontal object size of this section: 6.0 mm.