Hi all,
Well done to those that said limestone.
My son came up from Adelaide for 3 days so i took them out to Chillagoe and we all went through the "Royal Arch Cave".
Everyone on the tour had a good laugh at this formation (for obvious reasons). Apparantly in the past they have had written complaints demanding that it be removed. Got plenty of other pics and when i work out how to upload them i shall.
Cheers for now,
Duncan