UMD Geologists Explore Tasmania’s Hidden Gems
Four faculty members and graduate students traveled over 10,000 miles to Australia’s smallest state in pursuit of garnets, minerals with a rich geological history.
Lush vegetation. The scent of eucalyptus and tea trees carried on a breeze. The bizarre charm of long-snouted marsupials. These are just some of the natural wonders two faculty members and two graduate students from the University of Maryland’s Department of Geology observed on a recent research trip to Tasmania. But the group’s main focus was a different—and more literal—gem.
For a little over a week in January 2025, the four geologists traipsed through mud to collect garnets from woods, mines and coastlines in Australia’s smallest state, an island south of the mainland affectionately called “Tassie.” Garnets are a multicolored mineral widely used in jewelry and industry, but to geologists, they’re treasured time capsules containing secrets of Earth’s past.
One of the trip’s organizers, Geology Professor Sarah Penniston-Dorland, explained that garnets are found in many metamorphic rocks—those that transformed from one rock type to another under high heat, pressure or a combination of both.
“Rocks are in the Earth’s crust for a long time and garnet grows over a long period,” Penniston-Dorland said. “It doesn’t just crystallize in a short time, so it’s a useful recorder of the history that rocks have experienced.”
As part of ongoing research funded by the U.S. National Science Foundation, Penniston-Dorland and trip co-organizer and Geology Assistant Professor Megan Newcombe analyze the water content in garnets to explore a phenomenon called fluid flow during metamorphism. By developing a better understanding of how water moved through rock during periods of transformation, geologists can gain new insight into natural disasters like earthquakes and volcanoes and predict where precious metals might be concentrated in fluid.
The decision to visit Tasmania was prompted by a garnet sample the group received that stood out from the others.
“A collaborator gave us a sample and it was really promising,” Penniston-Dorland said. “We read about this particular locality in Tasmania and it looked like there was more complexity—and different generations—of garnets growing at different times and with different events of fluid flow.”
After landing in Tasmania’s capital city of Hobart, the researchers linked up with their host, geologist Ralph Bottrill of the Tasmanian State Geological Survey, and immediately got to work. On the first day, the group battled rain and big, biting flies in pursuit of garnet samples.
“It was this awful, rainy day and we were scrambling around in the mud and the woods, and I was thinking ‘Is every day going to be like this?’” Penniston-Dorland said with a laugh. “The weather improved after that.”
With their sense of adventure sated, the group turned to more sheltered sites, visiting both the Mornington Core Storage facility (a library of drill core and rock samples) and an active mine called Kara. At one point, geology master’s student Kathryn Bickerstaff (B.S. ’23, geology) donned a protective suit and respirator—a precaution against dust inhalation—and used a rock saw to extract samples.
In her research, Bickerstaff studies fluid-rock interaction in metamorphic rocks. She will now focus on samples collected from the Kara mine, adding that those garnets are “unique” because of their high water concentration and four distinct stages of mineralization.
“I feel very fortunate that so many mines welcomed us and allowed collecting,” Bickerstaff said. “Our guide, one of Tasmania’s state geologists, was one of the most knowledgeable geologists I have had the pleasure of meeting. We saw so many things in our short time there, both geologically and with the wildlife and landscapes.”
Geology Ph.D. student Kathleen Stepien uses her mineral samples to study how the water in garnet can help trace fluid flow in metamorphism.
“The Kara garnet crystals have been special because they contain a relatively large amount of water—up to about 5,000 parts per million,” Stepien said. “Measuring the major and trace element compositions will provide clues to help us determine what the fluid history looked like at this locality.”
By the end of the trip, the group amassed enough rocks containing garnets to fill seven suitcases. The rocks made it safely back to Maryland, but the group members nearly missed their flights home after a particularly spiky sample in Bickerstaff’s bag—a Tasmanian specialty called crocoite—triggered extra security checks.
“I brought about 40 pounds of material back, mostly geologically unique rocks,” said Bickerstaff, who is also an avid rock collector. “Most notable minerals that I brought back are pieces of crocoite and atlantisite. These minerals are found in very few localities, and it is very hard to get your hands on some here in the states.”
Now back at UMD, the geologists look forward to digging into these samples to discover the secrets within.
“We’re excited to start working on these samples,” Penniston-Dorland said. “Tasmania has such a diversity of interesting rock types and garnet, so it will be really interesting to see what we can learn from them.”
