Micro-World Gems & Gemology, Winter 2018, Vol. 54, No. 4

Rose in Demantoid from Madagascar

Rose-like inclusion in demantoid from Madagascar
Figure 1. A negative crystal growth blockage followed by an etch tube is observed in a faceted demantoid from Madagascar. The use of Rheinberg illumination gives the inclusion a red color reminiscent of a rose. Photomicrograph by Jonathan Muyal; field of view 1.99 mm.

Garnets have been known since antiquity. However, it was only during the late nineteenth century that the green variety demantoid—named for its “diamond-like” luster—was discovered in the Ural Mountains of Russia. A few decades later, Fabergé and other jewelers helped demantoid gain more exposure and popularity. Today demantoid garnet is found in various deposits around the world, including Russia, Namibia, Italy, Iran, Afghanistan, and Madagascar.

The authors recently examined a 0.33 ct round brilliant demantoid from Antetezambato, Madagascar—a skarn-related deposit—that was of particular interest for a large inclusion resembling a flower (see above). Further microscopic examination revealed the inclusion to be a growth blockage followed by a large etch tube.

The observed shape immediately evokes a flower in repose. The subtle oblique illumination also reflects a shadow on the opposite facet, adding more three-dimensionality to this “still-life” image. Finally, the use of Rheinberg illumination (Fall 2015 Micro-World, pp. 328–329) enhances the colors and gives the inclusion a suitable rose red color.

Even though horsetail inclusions are the more heralded internal feature of demantoid, the beautiful flower inclusion in this demantoid specimen from Madagascar proves once more that the exploration of the microscopic world in gemstones will always reserve for us endless surprises.

Jonathan Muyal is a research stone collection gemologist at GIA in Carlsbad, California. Pierre-Yves Chatagnier is with Tsara International in Paris.