Fuzzy yellow crystals discovered in an old uranium mine have been named caseyite in honor of William H. Casey, chemistry professor in the UC Davis College of Letters and Science.
“It was a complete shock and it made me smile,” said Casey, who was not involved in the discovery. “It made me a hero in the eyes of my 19-year-old son.”
The building blocks of caseyite are vanadium and aluminum compounds that have been a focus of research by Casey and his students for some 20 years.
“It’s really cool that these have been found in nature,” Casey said. “I spent two decades telling my fellow geochemists that these clusters are superb experimental models to test their ideas. Few listened and at least one said, 'Those aren't natural!'”
One of the caseyite building blocks is decavanadate, a vanadium-containing material that’s been studied for its potential as a diabetes treatment. Decavanadates are clusters of vanadium and oxygen atoms. The other main constituent of caseyite is almost identical to flat-aluminum 13 (flat-Al₁₃), a heretofore synthetic compound with uses in phone screens and electronics. Flat-aluminum 13 is a cluster of aluminum and oxygen atoms; in caseyite, the compound has a vanadium atom in place of three aluminum atoms. It’s the first time a flat-Al₁₃ compound has been found in a naturally-occurring mineral, Casey said.
Finding the compounds in a naturally occurring mineral could provide new research directions for scientists who grow decavanadates and aluminum clusters in the lab, Casey said. “This may lead to new approaches to making these things,” he said.
Just a little mustard please
In recognition of Casey’s research on decavanadates and aluminum clusters, Anthony Kampf, curator emeritus at the Natural History Museum of Los Angeles County, proposed naming caseyite for him. The name was approved by the International Mineralogical Association on May 4, 2019.
Kampf and his collaborators found outcrops of caseyite in three mines in Colorado that are part of the Colorado-Utah uranium-vanadium ore belt. The mineral forms on weeping tunnel walls where water moving through rock carries vanadium to the tunnel surface. Crystals of caseyite emerge as the water evaporates and vanadium reacts with oxygen in the air. This process, called efflorescence, is similar to how salt marks appear on basement or garden walls.
Vanadium gives caseyite its bright yellow color. “If you don’t look too closely, it looks like somebody spilled the mustard from their sandwich on the rock,” Kampf said. Up close, the mineral’s tiny, needle-sharp crystals look a bit like caterpillar fur, he added. “They really are quite unusual and beautiful.”
Kampf and his colleagues identified caseyite as a new mineral by using sophisticated scientific instruments to elucidate its unique composition and crystal structure. The team of mineral hunters included Mark Cooper and Frank Hawthorne of the University of Manitoba in Canada; John Hughes, University of Vermont; Barbara Nash, University of Utah; and Joe Marty, a collector. Together, the team has identified dozens of new minerals from the southwestern United States.
— Becky Oskin, content strategist in the UC Davis College of Letters and Science