INDONESIAN OPAL STONE
This is a piece of natural opal polished i purchased on my last trip to Banten. It has been cut on the opal field there. They have oiled the stone which is a common practice there as they dont polish the stone too well. The stone could be polished a bit better.
This stone is volcanic in origin. It is a common practice here for miners to heat the rough in sand to remove the clay which sticks to the rough and when polished they add a resin to get a better finish as it hides pits ect.