Synthetic opals have been produced and used in jewelry for more than three decades, and various imitation opals have been introduced in the trade. This article describes a new type of synthetic fire opal marketed as “Mexifire.” Some of the gemological properties of this synthetic are similar to those of natural fire opal. However, a low SG value (1.77) offers strong evidence of synthetic origin, and further indications are provided by a relatively low RI value (<1.40) and the presence of scattered pinpoints when examined with magnification.
