Born May 20, 1838, in Bonn; died there June 11, 1912. German geologist and petrographer.
Zirkel graduated from the University of Bonn, where in 1861 he also earned the Ph.D. degree. Beginning in 1863 he was a professor at the University of L’vov. From 1870 to 1909 he was a professor of mineralogy in Leipzig. Zirkel studied magmatic rocks in Iceland, Scotland, Italy, France, North America, India, and Ceylon. He was the first to use the crystal-optics method for the microscopic study and identification of rocks. Zirkel was the author of a textbook on petrography (1893–94), which went through several editions and promoted further development in petrography.