Bob,
Yes the rock was/is probably from around there. The rock and the image
have been removed by those who claim to have found it and they don't want
it looked at or analysed because of its spiritual value. (BS!)
I figured that it could be a simple photocopy heat transfer if the surface
was relatively flat or even some sort of selective dark toned cyanotype!?
Anyway the issue seems to have gone and I guess the farmer and his son are
the laughing stock of the town.
Regards,
Kevin Lock
Fremantle, Western Australia.