Dr. Ralph E. Van Alstine, 66, who retired last October as a commodity geologist for fluorspar in the Eastern Mineral Resources Branch of the U.S. Geological Survey, died Thursday at Georgetown University Hospital of complications from a kidney ailment. He lived in Bethesda.

During his tenure with the Geological Survey, which began in 1942, he was associated with extensive geological investigation of the mineral fluorspar in Newfoundland, Alaska and Colorado. He was the author of numerous articles for publications in his field.

Dr. Van Alstine was born in Paterson, N.J. He was a graduate of Hamilton College in Clinton, N.Y., where he was elected to Phi Beta Kappa. He received his master's degree from Northwestern University and his doctorate from Princeton University.

He was a member of the Geological Society of America, the Geological Society of Washington, and the Society of Economic Geologists. He belonged to Bethesda United Methodist Church.

He is survived by his wife, the former Nancy Warner of Bethesda; two sons, Peter, of Nashville, and David, of Altadena, Calif.; two daughters, Nancy, of Chicago, and Carol, of Missoula, Mont.; a brother, Lee, of Hawthorne, N.J., and a sister, Florence Alsdorf of Fort Plain, N.Y.

The family suggests that expressions of sympathy be in the form of contributions to the National Kidney Foundation.