The most widely spread of the sedimentary beds belong to the Miocene period.'
In Tertiary times the Central Plateau was the theatre of great volcanic activity from the Miocene, to the Pleistocene periods, and many of the volcanoes remain as nearly perfect cones to the present day.
The Miocene and Pliocene are absent.
It occurs in Miocene deposits and is also found washed up by the sea near Catania.
It is found in flat rolled pieces, irregularly distributed through a blue clay probably of Miocene age.