Jillian Banfield is a mineralogist who has contributed fundamental insights into the physical and chemical forces that shape the earth's surface. Her structural studies reveal the mechanisms of rock weathering, helping to explain how elements such as toxic heavy metals can accumulate within soil. She has shown that certain microbes living between rocks exert profound chemical effects on those rocks, both at the surface and deep below. These observations may lead to an enhanced understanding of soil and sediment formation, factors affecting water quality, and environmental processes as well as provide clues to the origins of life on earth. Her analyses of the interactions of rocks and microorganisms illuminate the impact of biology on the kinetics of mineral weathering; they also constitute a key step in understanding the ecology of these recently identified organisms. Banfield is a professor in the Department of Environmental Science, Policy and Management at the University of California, Berkeley. Previously, she was an associate professor of geology and geophysics at the University of Wisconsin, Madison, and was a professor at the Mineralogical Institute at the University of Tokyo. Banfield received a B.Sc. (1981) and a M.Sc. (1985) from the Australian National University, Canberra City, A.C.T., and an M.A. and Ph.D. (1990) from The Johns Hopkins University.