GIA’s First Research Intern: Genesis of a Gemologist

Young woman works with a Raman spectroscopy machine.
Rachelle Turnier used Raman spectroscopy and photoluminescence mapping to better understand the formation of basalt-related sapphires, the focus of her Ph.D. work. Photo by Kevin Schumacher/GIA.

Rachelle Turnier, GIA’s first research intern, began her undergraduate studies in geology, but a fellowship at the American Museum of Natural History turned her interests to gemology. Her work there with curator George Harlow on determining the geological origins of syenite-hosted sapphires made her realize that a geology degree could apply to the world of gems.

“Gemstones are beautiful minerals,” Turnier says. “Not too many geologists are gem-focused. There was obviously a hole that needed to be filled.”

GIA’s Research Internship Program is the first for undergraduate and graduate students. The Institute also offers the Richard T. Liddicoat Postdoctoral Research Associate Fellowship, founded in 2014, for postdoctoral researchers.

Turnier, who was a first-year Ph.D. student in geochemistry and petrology at the University of Wisconsin–Madison when she interned at GIA in late 2017, researched the geological conditions of basalt-related sapphire formation. Many sapphires are found in alluvial deposits after they weather away from the host rock, leaving only the geochemistry of the sapphires and their inclusions to give clues about their formation.

During her two-and-a-half-month internship, Turnier used GIA’s extensive gem reference collection to document zircon inclusions in sapphire samples, analyzing them with Raman spectroscopy to determine at what depths the stones formed. She also used photoluminescence (PL) mapping to determine whether spectroscopic and growth features unique to sapphires from different deposits exist, finding vastly different PL intensities between Thai and Cambodian sapphires. This shows promise as a factor that could aid in country-of-origin determination, but further studies are needed.

“We have field gemologists choosing samples from the source at all these deposits,” says Aaron Palke, a senior research scientist at GIA who worked closely with Turnier. “One of the things we want to do is to bring in outside researchers to help us find the most value in the gem reference collection.”

Turnier returned to the University of Wisconsin and is researching oxygen isotopes in the zircon inclusions and the host sapphire. Using a secondary ion mass spectrometer, she is working to determine when and through what geologic processes the sapphires and inclusions formed.
“I just love instrumentation,” Turnier says. “And what better thing to do than study pretty rocks and minerals on cool instruments?”

The one- to two-month Research Internship Program is offered at GIA’s Carlsbad and New York locations. Candidates should be pursuing a bachelor’s or graduate degree in physics, materials science, geology, chemistry, or a related field and must be in their junior year or higher. Selected interns will work on a defined project and be mentored in spectroscopy and gemology by GIA research scientists and gemologists. A project conclusion will be reached by the end of the internship. An extension of the internship is possible.

Three interns are at work in the Carlsbad laboratory in 2018, studying color in ruby and sapphire, color in copper-bearing feldspar, and the spectroscopic signatures of yellow diamonds from Canada. The New York lab recently hosted an intern focusing on point defects in mineral-included superdeep type IIa diamonds from Juina, Brazil, and, early next year, a second will investigate color-forming defects in unusual yellow- and brown-grained type IaAB diamonds from Botswana.

Find out more about the GIA research internship program, qualifications, and application process.

Erin Hogarth is a writer and editor at GIA in Carlsbad, California.