An opalescent Belemnite fossil from the Jurassic period, Cooper Pedy, South Australia. Similar to the modern squid, the Belemnite is an extinct marine cephalopod. From its aragonite phragmacone would emerge arms equipped with small hooks for grabbing prey passing in the prehistoric waters. Flourishing in the Jurassic and Cretaceous periods, their remains are found throughout the world, but only in the abundant opal fields of South Australia are they found in this special form. Geomorphically replaced over millions of years by precious opal, the shell now flashes with opalescent green, pink and purple and thanks to opal’s microcrystalline structure the smallest details have been preserved. (Source) @sixpenceee