Snowflakes in Opal
Recently, the author examined a 6.85 ct black opal cabochon, likely from Ethiopia due to the digit pattern of its play-of-color (B. Rondeau et al., “Play-of-color opal from Wegel Tena, Wollo Province, Ethiopia,” Summer 2010 G&G, pp. 90–105; B. Rondeau et al., “On the origin of digit patterns in gem opal,” Fall 2013 G&G, pp. 138–146). This opal contained several inclusions, such as black spots concentrated along pits and scratches, indicating that it was treated to produce a darker color and enhance the play-of-color phenomenon. Additionally, metallic octahedral crystals were identified as pyrite by Raman analysis. Interestingly, fiber-optic illumination revealed whitish snowflake inclusions (see above), which were identified as aragonite through Raman analysis. To the author’s knowledge, these are the first documented aragonite snowflake inclusions in opal.
