Micro-World Gems & Gemology, Spring 2022, Vol. 58, No. 1

“Fishbone” Inclusion in a Burmese Peridot from Mogok

Burmese peridot exhibits fishbone-like inclusion.
The fishbone-like inclusion in the Burmese peridot. Photomicrograph by Shu-Hong Lin; field of view 1.32 mm.

Recently, an 83.25 ct cushion faceted peridot with medium dark yellowish green color and good clarity was sent to the Taiwan Union Lab of Gem Research (TULAB) for identification service. This peridot, reported by the owner as from Mogok, Myanmar, was relatively rare in the Taiwanese market because of its impressive size, color, and clarity. Microscopic examination revealed a few short needle inclusions and a fishbone-shaped inclusion (see above), the latter of which is common in peridot from this origin. The backbone appeared to be a long prismatic crystal with some vertical cleavage planes along it, while the smaller branches were composed of parallel tabular inclusions that might result from epitaxial exsolution. Due to peridot’s strong birefringence, brightfield illumination and plane polarized light were adopted to reduce the interference and obtain clear microscopic images.

Shu-Hong Lin is chief gemologist at the Taiwan Union Lab of Gem Research in Taipei.