Tom...long ago I hade a good time fossicking for opal in Lightning Ridge. Best place to find them. I kept a few "raw" just for memmory we never find speciment like yours. I have some cut  and polished as well, most of them triplets, I have one big solid white thou. 

Boji stone? http://en.wikipedia.org/wiki/Boji_stone I did hear about it but didn't know much of it....I don't have one but as from now on it is on my list to get it.

seeya  Tunde