This is a Koroit Boulder Opal Pendant from the Koroit Opal fields of Queensland, Australia. It has been fitted with a 925 Sterling Silver Bail and has a leather like adjustable strap fitted; ready to use as a pendant.
If you see an opal on this website that you might like to have as a pendant, please contact Peter to discuss if it is possible with that particular stone.
You also need to state if you wish to have a bail fitted or not. If you do, then you would need to be charged for the cost of metal, silver or gold.