Just following on from my previous post about bodytone. This picture shows two opals. See the difference between crystal opal and white opal. The white opal on the right has a cloudy appearance to the opal, where the crystal opal on the left is a little more crisp and clear. The bodytones are only one scale different. You could get away with calling the opal on the right a crystal opal and obviously the opal on the left is a true crystal opal.