The Gem Detective

When Aaron Palke is on the case, no stone remains unturned.

March 2023

Reading time min

Aaron Palke searching through many green-colored stones

GREEN SCREEN: Gemologist and researcher Aaron Palke examines newly mined demantoid, one of the rarest varieties of garnet, on location in northern Madagascar. Photo: Gemological Institute of America

Every so often, Aaron Palke realizes he’s holding a small stone worth more than his house. A steady stream of diamonds, emeralds, and rubies flows through his lab in Carlsbad, Calif. But knowing exactly what he’s holding can be difficult, and for Palke, that’s the fun of it. His is detective work, using microscopes, spectrometers, and trace element chemistry to piece together the story of a gemstone.

Palke, PhD ’14, is a researcher at the Gemological Institute of America (GIA), a nonprofit organization that works to protect the public’s trust in the gem and jewelry industry, in part by certifying gemstones’ color, clarity, carat weight, measurements, and place of origin. An expert in the geology and geochemistry of colored stones, Palke develops techniques for detecting whether a gem has been treated—that is, had its natural appearance enhanced. Emeralds, for example, are commonly treated with cedarwood oil, which fills in fractures and improves transparency. 

Aaron Palke looking close-up at a gemINSPECTOR GADGET: Palke uses a jeweler’s loupe to view aspects of a stone that are difficult or impossible to see with the unaided eye. (Photo: Gemological Institute of America)

Gemologists can see evidence of oil in a treated emerald, but other types of treatment can be difficult to discern. “There are,” Palke says, “some calls we can’t currently make.” A bright, pure red ruby might have developed its desirable color through exposure to high heat, a treatment that’s not always detectable. Unheated, a ruby of the same hue would command a premium. And untreated stones hold mysteries of their own. Sapphires from Madagascar can appear identical to those from Sri Lanka, even when viewed through a microscope. “My job is to research ways to be more accurate with our calls,” he says. 

Palke, who particularly enjoys working with sapphire, garnet, and turquoise, is living out his rock-collector childhood dreams at the GIA. “I get to see the most fascinating, most beautiful stones that I would never get to see anywhere else,” he says. “For this very brief period in time, I get to study that stone. I get to look inside of it, understand the stone, and analyze it. It’s just a privilege to be able to learn [its] story.”

Kali Shiloh is a staff writer at Stanford. Email her at

You May Also Like

© Stanford University. Stanford, California 94305.