writes "One of the six giant — 27 feet across, 20 ton — circular mirrors that will be part of the 4,000 sq. ft., Giant Magellan Telescope that ultimately look for stars, galaxies and black holes has been polished and completed — now for the other five. The mirrors will form the heart of the 25-meter Giant Magellan Telescope, and when complete will provide more than 380 square meters, or 4,000 square feet, of light-collecting area."
This is a big project, not just a big mirror. From the article: "At the Carnegie Institution for Science's Las Campanas Observatory in northern Chile, earthmovers are completing the removal of 4 million cubic feet of rock to produce a flat platform for the telescope and its supporting buildings. The telescope is scheduled to come online in about 10 years.