“Worms” in Opal
Near-colorless heulandite crystals resembling worms in an Ethiopian opal exhibiting play-of-color. Photomicrograph by Bawornluk Keeratithanarut; field of view 2.88 mm.
Opal is an amorphous gemstone known for its unique play-of-color phenomenon. Additionally, opal hosts a wide range of mineral inclusions. Recently, an interesting inclusion was observed in a 22.96 ct Ethiopian opal. Standard gemological testing and Fourier-transform infrared spectroscopy confirmed the opal as natural and untreated. Microscopic examination revealed the presence of near-colorless crystal inclusions (see above), matching heulandite of the zeolite group when identified by Raman spectroscopy. These inclusions exhibited a distinctive morphology, resembling worms with elongated, segmented bodies. In some areas, the inclusions appeared twisted, further enhancing their serpentine illusion.
