Thanks Christine

I've been looking at some Carn, and I think I can discount that now. Tremaen is a different type of clay I think.
I've seen a couple of pieces of Troika in a collectible's window, so next time I'm passing I'll have a good look, and may be bend the vendor's ear. I've never actually handled a piece of Troika so don't know anything about it, other than what I've seen in books, ebay etc.etc.