Caltech Mourns the Passing of George Rossman (1944–2026)

George Rossman (PhD '71), professor of mineralogy, emeritus, passed away on February 6, 2026. He was 81.

Rossman was born on August 3, 1944, in La Crosse, Wisconsin. He spent his childhood in Eau Claire, Wisconsin, a lumber town in the state's densely wooded northwest. Rossman cultivated a passion for the natural sciences throughout his childhood, collecting minerals, interacting with the chemistry department of the nearby Wisconsin State College, and building a home chemistry laboratory in his basement. He graduated from his high school class as the salutatorian in 1962 and went on to study at the newly formed Wisconsin State University–Eau Claire, graduating with a BS in chemistry and mathematics in 1966.

Rossman came to Caltech to pursue graduate work in inorganic chemistry, joining the lab group of Harry Gray, now the Arnold O. Beckman Professor of Chemistry. At that time, Gray's group studied the electronic structures of compounds containing transition metals, and Rossman contributed to that effort through his thesis research on the spectroscopic and magnetic properties of molybdates and other transition metal materials.

Rossman received his PhD in 1971 and was immediately recruited by the late Robert P. Sharp (BS '34, MS '35), professor of geology, and the late Eugene Shoemaker (BS '47, MS '48), professor of geology and planetary science and chair of the Division of Geological and Planetary Sciences (GPS) at the time, to serve as lecturer in mineralogy—a staple of the division's undergraduate program. Rossman's passion for the subject and infectiously charismatic teaching contributed to the division hiring him as an assistant professor of minerology that same year. He was awarded tenure in 1977, promoted to Full Professor in 1983 and served as the McMillan Professor of Mineralogy from 2008 to 2015. He was the division academic officer for GPS from 1999 to 2008.

Rossman's colleagues note that he was proud of the fact that he had never taken a geology class. Despite this lack of imprimatur, Rossman's fascination with the fundamental structures and properties of natural materials guided him to a groundbreaking career, including several contributions that led to first-order advances in understanding Earth and planets.

The unifying theme of his research career was a simple, relatable question: Why do gems and other minerals possess their distinctive colors?

To answer this question, Rossman brought to geology a set of analytical technologies from the field of chemistry, along with a deep understanding of chemical physics. The most important of these technologies was Fourier-transform infrared spectroscopy (FTIR), a technique to obtain infrared spectra from samples. This process emerged as a widely available technology during the first years of Rossman's career, and he was the central figure responsible for demonstrating the importance of FTIR spectroscopy in understanding complex natural solids, and in using that technology to solve the mysteries of mineral colors and connected wider problems in Earth and planetary science.

A major aspect of Rossman's research was his exploration of the distribution of small quantities of dissolved water and other forms of hydrogen in the minerals that are abundant in the deep earth. Rossman's studies led to transformations in our understanding of Earth's water cycle, melting, and volcanism, and the creeping flow of rocks that makes plate tectonics possible. Early in his career, Rossman explored the spectroscopic features of an exotic hydrous iron sulfate mineral, Jarosite—now understood to be an essential material of the Martian surface. The ongoing spectroscopic study of the mineralogy of the Martian surface is a legacy of this work. Rossman also created and maintained the Caltech Mineral Spectroscopy Server—an open-access resource used by the global mineralogy community—and paved the way for the modern classification and authentication of gems.

For these and other contributions, Rossman received the inaugural Dana Medal of the Mineralogical Society of America (MSA) in 2001. This was followed in 2021 by the MSA's highest award, the Roebling Medal. Other awards include the Friedrich-Becke Medal of the Austrian Mineralogical Society and the Lifetime Excellence Award from his alma mater, the University of Wisconsin–Eau Claire. Multiple minerals in the tourmaline family were named in his honor: Rossmanite, Alumino-Oxy-Rossmanite, and Fluor-Rossmanite.

Rossman will be remembered for his contributions to education at Caltech, which spanned 55 years and impacted thousands of students. In 2004, he was recognized for his exceptional instruction in the classroom with the Richard P. Feynman Prize for Excellence in Teaching, Caltech's highest teaching prize.

A full obituary is to come.