One of my favorite books at the moment is "Opal The Phenomenal Gemstone". This book has an in depth look at the opal gemstone, where it's found, and how it's mined. The book also features opal fossils found from the Australian opal fields of Coober Pedy, Andamooka, White Cliffs and Lightning Ridge. These fossils are from the Cretaceous period, notable for being the time of the Dinosaurs. The fossils found at Lightning Ridge are different to those of the other opal fields as Lightning Ridge represent a terrestrial environment with freshwater depositional setting. Where the other opal fields are marine depositional environments.
