It was cheap but cut fairly symmetrical

Just set this little beauty, what would you describe the stone as?

Large flat faced Allens Rise Opal with a mixed fire pattern. Flag Stone to broad flash fire of green and blue with hints of orange. Set as a pendant for best colour and pattern. - Mine - Allens Rise - Body Tone - N6 - Brightness - 4.5 - Fire colour - Green Blue Orange - Size - 28x18x5.7mm - Weight - 21.70 carats

The pin fire pattern is very cool.

Perfect example of a white opal showing the rare Mackerel sky fire pattern.