Mieno,
Im surprised no-one responded.
Mate I've dug up the following, just in case:
Pottery Supplies Homepage. ph 33682877. They're at Milton.
I was quoted the following: (grades unspecified):-
7.6m x610 of ceramic insulation, $145.
25kg of cement fondue, $86.
We lit the first of the curing fires tonight: awesome. Wish I knew how to post images, because it really is so gratifying to see one's creation come to life and breathe.
btw, we stayed low-tech. I won't bore you with detail. Your pumice would be ideal as a component in foundation concrete. You'll possibly need a couple of bags of vermiculite ($20-27 per 100L bag here in Bundy. Try your nursery suppliers, and DON'T believe any Einstein floor walker who claims 5L bags are standard issue.
Gopher mate: all good. And minor blemishes can be fixed/ignored, eh.
Jeff.