Dr. Frank S. Grimaldi, 69, a retired chief chemist and an expert on mineral analysis with the U.S. Geological Survey, died of Alzheimer's disease April 30 at the Manor Care Nursing Home in Arlington. He lived in Annandale.

Dr. Grimaldi was born in Italy. He came to this country in 1922 and settled in New York City. He graduated from what became the City University of New York, where he also earned a master's degree in chemical engineering. He received his doctorate in inorganic chemistry at the University of Maryland.

He moved to the Washington area in 1940 and joined the Geological Survey. During his career, he conducted research on the chemical analysis of ores, rocks and minerals, especially for trace and rare elements. He participated in the Manhattan Project, which developed the atom bomb in World War II, and later supervised analytical work for the Atomic Energy Commission.

From 1952 to 1962, Dr. Grimaldi taught chemistry at George Washington and American universities, in addition to his duties at the Geological Survey. He retired in 1971 and moved to California. He returned to the Washington area in 1984.

Survivors include his wife, Gloria, of Annandale; a daughter, Dr. Karen Hickman of Vienna, and a sister, Louise Frati of Moorestown, N.J.