8.14 carat boulder opal with bright flashes of blue, green, and orange.
 
Shape:  Irregular (roughly rectangular)
Color(s):  Remarkably colorful rainbow boulder with bright blue, green, and orange flashes
Brightness:  B4
Body tone:  n/a
Dome:  n/a
Dimensions:   23.7mm x 8.8mm
Source:  Lightning Ridge