Michael Fleischer was born on 27 February 1908 in Bridgeport, Connecticut, the son of Hungarian Jewish immigrants.

From 1934 to 1936 he was an assistant to Professor William Ebenezer Ford (1878–1939) and helped prepare a revision of James Dwight Dana's System of Mineralogy.

[5] In a 1944 paper Fleischer showed the importance of the manganese oxide mineral nsutite as a component of dry cell batteries.

[1] Between 1944 and 1947 Fleischer led a group of researchers into raw materials for the Manhattan Project, including uranium, thorium and secondary products of atomic fission.

His team prepared restricted reports on the geochemistry of gallium, gadolinium, beryllium, germanium, indium, niobium and tantalum.

Fleischer was the coauthor with Judith W. Frondel of a glossary of minerals bearing uranium and thorium, published in four editions in 1950, 1952, 1955 and 1967.

[4] In the Fall 1970 issue of The Mineralogical Record Fleischer proposed in Some possible new minerals not yet found that BaF2 might exist in nature, but probably not in association with the highly soluble sulfate, phosphate or carbonate phases of barium.

[7] For example, in 1956 Fleischer noted that bursaite's X-ray data shows many coincidences between those of the minerals kobellite and cosalite.

[4] The book is an important reference work that lists mineral species, their formulas and their crystal systems.

[2] Fleischer developed Alzheimer's disease and spent his last two years at the Hebrew Home of Greater Washington, where he died on 5 September 1998 at the age of 90.