Natural History - Cut and Polished Agate Crystal Geode Section Group

A stunning fossil bivalve shell, preserved in black opal, showing iridescent colours, including blue, greens and reds. 15.2 grams total, 41 x 34 mm including case

Fine condition.

From Lightning Ridge, Australia. Private Shropshire, UK collection.

Opal is a spectacular gemstone, and a dazzling key to Australia’s mysterious past, because buried in the Australian opal fields are fossils of dinosaurs and other strange creatures that lived 110 million years ago, in Early Cretaceous times. These fossils are literally gems: teeth, bones, shells and pinecones which have turned to solid opal. Australia is the only country where opalised animal fossils are found. Opalised fossils are rare and precious; even more so because in Australia, it is rare to find fossils of any kind from the time of the dinosaurs.

A fossil Diplomystus sp. fish in a matrix. 500 grams, 16.5 x 11.7 cm



From the Green River Formation, Lincoln County, Wyoming, U.S.A. From an old Lincoln, UK, collection.

Seasonally, some 56 million years ago, in the Green River Region of Wyoming, torrential rains fell on the mountains. The rain flowed down the mountain sides, forming wide shallow lakes in the valley below. During the dry season, these lakes evaporated (similar to certain parts of Africa today). Millions of fish died in this short period of time. This climatic cycle happened over a 20-thousand-year period. Layer upon layer of mud was deposited over these years, entombing huge numbers of fish. At a much later date volcanic activity uplifted this area to expose their fossils.

A group of two fossil ammonites, polished to one face. 416 grams total, 7.5-11.8 cm



From Scunthorpe, UK. Ex Lincolnshire, UK, collection.