Belemnite, opalized fossil pipe squid, from Coober Pedy (South Australia). Green, red , blue and a little yellow. The sandstone inclusions show the natural stone. Drilled and ready to be worn on a leather cord or choker. Could also be set into a pendant.
Opal weight is 16.1 ct and size is 7.22 x 10 x 31.55 mm.