Here is a beautiful and unique boulder opal specimen from my mine in Koroit, Queensland, Australia. Yes, it is completely natural. I found it, cut it and polished it. Boulder opals with these magnificent combinations of patterns and colors only occur in a very small area of southwest Queensland - and pieces like this do not occur very often even in Koroit.
Approximate mass: 209 grams
Approximate dimensions: 82.1mm x 73mm x 28.2mm
More photos are available on request.
The video quality might be better if you view it on youtube directly and click the HQ button (the quality of the video seems to be better when using Firefox as a browser instead of Internet Explorer) -
Link to youtube video (or copy & paste in your browser):
http://www.youtube.com/watch?v=zIH8YGssuSM