The three Owyhee River thundereggs I have seen are all so different that I hardly know where to start with classifying them. The Owyhee Blue Opal is quite famous, and I think that is what this specimen is a sample of, though how fine a sample I have no idea. This is a very simple thunderegg - just a pocket of somewhat 'crazed' (ie. cracked) opal in a simple brown matrix.