Micro-World Gems & Gemology, Winter 2020, Vol. 56, No. 4

Quarterly Crystal: Garnets in Aquamarine

John Koivula

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This blue-green aquamarine crystal weighs 26.16 ct.
Figure 1. This aquamarine crystal plays host to several orange garnet crystals. Photo by Angelica Sanchez.

For this quarterly crystal, we examined a transparent light blue-green hexagonal prism of aquamarine beryl terminated with a flat pinacoid (figure 1). The crystal weighed 26.16 ct with corresponding measurements of 25.93 × 11.64 × 9.08 mm. This aquamarine reportedly came from the Shigar Valley in the Skardu district, Gilgit-Baltistan territory of Pakistan, an area known to produce gemmy aquamarine crystals.

Raman identified these inclusions as spessartine.
Figure 2. The garnets in the aquamarine were identified by Raman analysis as spessartine. Photomicrograph by Nathan Renfro; field of view 9.40 mm.

Magnification revealed numerous intense orange syngenetic garnet crystals near the base of the aquamarine. Raman analysis of the well-formed garnets identified them as spessartine (figure 2).

Garnet inclusions in beryl are rare. Having the opportunity to study this euhedral crystal gives us further insight into the pegmatitic origin of this aquamarine and its locality.

John Koivula is an analytical microscopist at GIA in Carlsbad, California.