The value of a fire opal is based upon the desirability and uniformity of its color, with yellow being on the low end of value and red being on the high end.
Transparent stones are preferred over translucent stones. The best fire opal typically sells for prices that are much lower than the best precious opal; however, fire opal specimens with exceptional color will sell for higher prices than some specimens of precious opal with less impressive play-of-color.
