All seven of the 8.4m mirrors for the Giant Magellan Telescope in Chile are cast and polished at the Richard F. Caris Mirror Lab at the University of Arizona. At the present time, four mirrors in various stages in the process including casting, grinding and polishing. Each mirror uses more than 38,000 pounds of carefully selected glass blocks. Each is polished to match the shape of the parabolic mirror surface to an average of 1 micron so the GMT can produce images 10 times sharper than the Hubble Space Telescope.
Photos: Mirrors for Giant Magellan Telescope at UA mirror lab