Brightness

The brightness of the fire coming out of an opal is one of the most important contributors to its beauty and value. The fire is also the most difficult characteristic to judge consistently. One reason for this is that people cannot keep the degree of brightness of a gemstone accurately in their minds for an extended period of time. There is a tendency to elevate the brightness of the gemstone the person is currently examining in comparison to others seen previously. The other reason is that brilliance is seriously affected by the light under which the opal is viewed. This is why some opal sellers use those little high power lamps. They make an opal appear brighter than it would appear in natural sunlight, thus giving the impression that the gemstone is of greater brightness than it really is, implying a greater market value. Remember, brightness is the amount of light coming back from the opal. Moving the opal away from the light gives you an idea of how well the brightness holds as lighting changes.