The sharp outline of a tabular included crystal in a 0.44 ct red spinel (see above) appeared suspended when viewed with darkfield illumination. Under fiber-optic lighting, the body of the crystal darkened and displayed a flash of rainbow colors caused by thin-film interference between the host spinel and the inclusion.
Not all included crystals display such drastically different appearances with different light sources. This particular well-formed crystal was the only notable inclusion in the red spinel. The surprising “rainbow” effect made it stand out from other crystal inclusions observed in similar material.
Isabelle Corvin is a gemologist in Olympia, Washington.
The sharp outline of a tabular included crystal in a 0.44 ct red spinel (see above) appeared suspended when viewed with darkfield illumination. Under fiber-optic lighting, the body of the crystal darkened and displayed a flash of rainbow colors caused by thin-film interference between the host spinel and the inclusion.
Not all included crystals display such drastically different appearances with different light sources. This particular well-formed crystal was the only notable inclusion in the red spinel. The surprising “rainbow” effect made it stand out from other crystal inclusions observed in similar material.
Isabelle Corvin is a gemologist in Olympia, Washington.
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