He became inspector-general of mines, and director of the Geological Survey of France. He was distinguished for his researches on extrusive rocks, their microscopic structure and origin; and he employed the polarizing microscope early on for the determination of minerals. In his many contributions to scientific journals he described the granulite group, and dealt with pegmatites, variolites, eurites, the ophites of the Pyrenees, the extinct volcanoes of Central France, gneisses, and the origin of crystalline schists.
He wrote Structures et classification des roches éruptives (1889), but his more elaborate studies were carried on with F Fouqué. Together they wrote on the artificial production of feldspar, nepheline and other minerals, and also of meteorites, and produced Minéralogie micrographique (1879) and Synthése des minéraux et des roches (1882). Levy also collaborated with Alfred Lacroix in Les Minéraux des roches (1888) and Tableau des minéraux des roches (1889).