This is a natural piece of shell opal fossil. . 100 million years ago inland Australia was a vast sea. The shell voids were replaced over time by opal making a unusual rough.You will find the stone slightly curved as it follows the shape of the shell so care should be taken when setting.It can also be made in to doublets.
Mined in Coober Pedy Sth Australia.
photo taken wet
I have thousands of rough stones in my store SEDA ROUGH OPALS but you can only combine with stock in this store. I suggest you look at the rough dry and wet before cutting as we only refund on untouched rough. [sorry not set up to work between stores}