This is a piece of natural rough opal i purchased on my last trip to Banten. Indonesia.
This opal is volcanic in origin and this was a wood fossil replacement.
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.
We have taken a photo of the stone dry to show the colour.
Note this opal loves strong sunlight to looks its best-in dim light there will be little colour,