Suspended Crystal in Red Spinel
A crystal inclusion in red spinel shown in darkfield illumination (left) and fiber-optic lighting (right). Photomicrographs by Isabelle Corvin; field of view 1.78 mm.
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.
