Adolph Knopf (December 2, 1882 – November 23, 1966) was an American geologist. Educated at the University of California, Berkeley, he held professional appointments at the United States Geological Survey, Yale University, and Stanford University. He was primarily a petrologist and mineralogist, though later in his career contributed to geochronology. He performed much of his field work in the western United States, investigating mineral deposits in Alaska, the Boulder Batholith in Montana, and the Gold Country of California. Knopf was a member of the National Academy of Sciences and the American Academy of Arts and Sciences. He served as president of the Geological Society of America in 1944 and received its Penrose Medal in 1959. His second wife, Eleanora Knopf, was a notable geologist and frequent collaborator. Early life Knopf was born December 2, 1882, in San Francisco, California, to German American immigrants. His father was a building contractor. He grew up with his family on a ranch near Woodside, California. Career Knopf entered the University of California, Berkeley, where he became a student of petrology under Andrew Lawson. He earned a Bachelor of Science degree in mining geology in 1904 and a Master of Science degree in 1905. That same year he spent the first of six summers surveying the mineral deposits of Alaska for the United States Geological Survey (USGS). In 1906 he moved to Washington, D.C., to work for the USGS full-time. The Alaskan Division, of which Knopf was one of about a dozen members, was considered the best geologic group in the USGS at that time. Knopf's work on tin deposits in the Seward Peninsula became the basis of the dissertation for his Ph.D., which he received from Berkeley in 1909. In Alaska he also discovered the minerals hulsite and paigeite. In 1911 Knopf was promoted from assistant geologist to geologist. Over the next nine years he undertook a series of field projects for the USGS, beginning with the mining district in Montana that includes the Boulder Batholith and continuing to other western states including Nevada and California. In the latter state he surveyed the Gold Country. After discovering that universities on the eastern seaboard were paying about double the USGS salaries, Knopf left the USGS for a teaching position, and a number of his colleagues followed suit. Knopf began at Yale University in January 1920. He encouraged students to work with the USGS as he