Auguste Michel-Lévy

http://en.wikipedia.org/wiki/Auguste_Michel-L%C3%A9vy

Auguste Michel-Lévy (7 August 1844 - 27 September 1911) was a French geologist. He was born in Paris.

He became inspector-general of mining|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).

Michel-Lévy pioneered the use of birefringence to identify minerals in thin section with a petrographic microscope. He is widely known for the Michel-Lévy interference colour chart, which defines the interference colors from different orders of birefringence.

He also created classification schemes for igneous rocks which accounted their mineralogy, texture, and composition, and showed that igneous rocks of different mineralogies could be formed from the same chemical composition, with different conditions of crystallization.