This is a nice specimen of Opal-AN found in Sebastopol, a suburb of Ballarat from a find in 2013, the site is no longer accessible.
This specimen shows transparent, colourless Hyalite opal in little balls and 'mushrooms' all over one side of a chip of grey basalt. The opal sits out off the stone a bit and shows interesting form In places the stone looks wet with opal. There are other micro species on this one too including tiny Augite crystals.
Specimen is 28mm x 20mm by 11mm.