This is a Solid Natural Crystal Gem Opal from Coober Pedy in South Australia, which would suit being set in a ring or pendant. It is slightly transparent and shows multi colours. It can only be truly appreciated in natural light when the colours come flashing out.
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.