The products of Kyocera Corp. that show play-of-color were investigated to determine if the materials are truly synthetic opal or rather are opal simulants. The authors propose that, because these materials contain no water, they do not match the composition of natural opals and, thus, should be designated opal simulants. The gemological properties of the samples examined are also provided, including those by which the Inamori material can be separated from natural opal.
