This is an unusual natural matrix boulder opal, which is polished and ready to be mounted or displayed.
It is an oval shape, 20mm by 13mm, 2mm thick and of 6.40 carats. It is polished on the upper surface.
It has small opal veins and patches formed within the brown ironstone, which flashes green, yellow and red.
An interesting opal which could be used to make a unique pendant or large ring.