Professional Jeweler Archive: Mirage Inclusion

October 2000

Gemstones & Pearls/Gemology

Mirage Inclusion

Internal structures may also look like a cocktail

Because of their brownish, yellow or russet tones, hessonite garnets are easily confused with the spessartite variety. In gemological literature, hessonite – a rare variety of grossular garnet – has been described also as a “cinnamon stone.”

It could just as easily be dubbed a whiskey-and-soda or a mirage stone. Visual examination, often at close range but best through a microscope, shows an internal structure that resembles whiskey and soda as seen through a tumbler or the shimmering horizon in a scorching desert. Caution: It’s probably best to be sober when describing hessonite’s appearance.

The shimmering, oily aspect easily distinguishes hessonite from spessartite. Gemologists say this optical feature is due to the garnet containing partially fused transparent inclusions with rounded outlines – possibly apatite or zircon. Because the refractive index is similar to that of garnet, the apatite inclusions don’t stand out in strong relief.

A toast to hessonite!

– by Robert Weldon, G.G.

Most hessonites come from Sri Lanka and are found as a byproduct in the search for sapphires and rubies. At 30X (inset) the shimmery appearance of the inclusion is much more pronounced.

Copyright © 2001 by Bond Communications