Belemnite Opal
Belemnite opal is a fossilised belemnite, an extinct squid like marine creature from the Cretaceous period, where the original shell has been replaced by precious opal over millions of years, preserving the bullet shape of the fossil while displaying full play of color. These stones form when silica rich groundwater seeps into buried belemnite fossils and slowly replaces the calcium carbonate with opal, mainly in the South Australian opal fields of Coober Pedy, Andamooka, and Mintabie. Belemnite opal is highly collectible because it combines a complete marine fossil with precious opal in a single stone, making each piece both a gemstone and a natural history specimen. Below is a full guide to belemnite opal, covering how it forms, where it is mined, and what makes it valued by collectors and investors.
Belemnite Opal is an opalized, fossilized squid primarily found in Coober Pedy, South Australia. These fossilized opals, formed over approximately 100 million years, are rare. Belemnites, an extinct order of squid, inhabited the late Triassic to late Cretaceous periods. Unlike modern squid, Belemnites possessed internal skeletons. They were equipped with ten hooked arms for hunting and grasping prey, potentially regenerating up to 800 arms. Belemnites were prolific reproducers, laying eggs ranging from 100 to 1000. While some species thrived in turbulent open oceans, others inhabited calmer seabeds. The largest recorded belemnite measures approximately 70cm in length.
A significant discovery of Belemnites occurred in Coober Pedy, South Australia. While most specimens exhibited a white body tone with minimal colouration, some displayed remarkable opalization, intricate patterns, and vibrant hues. Read more about opal brightness and body tone guide
