It’s not every day you come across a gemstone that brings together two of the trade’s most treasured varieties—emerald and alexandrite—in a single, faceted stone!
While these two chromium-colored gems can form under similar conditions and may be mined from the same general area, finding them grown so closely together that they can be cut as one is exceptionally rare—and truly an amazing find.
In this article, Kaylan Khourie, FGA, of Lotus Gemology, shares the story of a 15.80-carat pear-shape, one gem that is both an emerald and an alexandrite. Bought as a piece of rough, the stone revealed its secret only at the polishing wheel: an intergrowth of more than one mineral. What follows is a close look at this remarkable gem—and the geological recipe that made it possible.
An Alexandrite-Emerald Intergrowth, Reportedly from Russia
Kaylan Khourie, FGA, Lotus Gemology
Although many emerald deposits also produce alexandrite, particularly those formed in association with mica-rich schist, it is rare that both gems are found in such a close association that they can be fashioned into a single stone. This article details the examination of one such piece, reportedly originating from a deposit in Malysheva, Russia.
Alexandrite and emerald are the Cr/V-bearing varieties of chrysoberyl (BeAl2O4) and beryl (Be3Al2Si6O18), respectively, although Fe can also affect their coloration. The main chemical difference between the two minerals is that chrysoberyl lacks Si, which is a major constituent of beryl. In general, alexandrite and emerald are geologically rare because they require the simultaneous presence of both Be and Cr. While Be often occurs in geochemically ‘evolved’ rocks such as granitic pegmatites, Cr is commonly associated with mafic-ultramafic rocks. The intrusion of pegmatites into these rocks can result in the formation of mica-rich schist in the contact zone, and this is typically where alexandrite and/or emerald may crystallize. In some cases, alexandrite may occur together with emerald in these schist-hosted deposits (Giuliani et al., 2019; Sun et al., 2019). The close association of these gems has been described for various localities, including Malysheva, Russia (Schmetzer, 2010).
In September 2024, a 15.80 ct pear-shaped gemstone was submitted to Lotus Gemology’s Bangkok laboratory for identification. The specimen, reportedly from Malysheva, was purchased in rough form by the client, who later discovered during the cutting process that it consisted of an intergrowth of more than one mineral.
The stone was first examined with a gemological microscope and then analyzed with confocal microRaman spectroscopy. These techniques showed that it consisted of about 75% translucent alexandrite, which was split into two sections: a large portion at the round end of the pear and a smaller area near the tip. Between the two was a zone of transparent emerald. A vein of phlogopite mica was present at one of the alexandrite/emerald boundaries, along with zoned particle clouds.
Tap here to read Khourie‘s complete research at Lotus Gemology!
ABOUT THE AUTHOR
Kaylan Khourie is a South African gemologist with a decade of laboratory experience focusing on diamond, corundum, beryl, tanzanite and many other gemstones. A Fellow of the Gemmological Association of Great Britain (FGA) since 2017, Kaylan has since gained a special interest in unique gems, rare synthetics and abnormal treatments. He is a big football fan and enjoys spending quality time with his family. Kaylan joined Lotus Gemology in early 2023. In 2024, Kaylan co-authored Broken Bangle • The Blunder-Besmirched History of Jade Nomenclature.
