The 25 m aperture Cornell Caltech Atacama Telescope (CCAT) will be the first segmented telescope of its size and precision. A new technology was required to be able to economically manufacture the segments for the primary mirror. This technology had to be a low cost, low risk, volume manufacturing process in addition to meeting all of the optical and mechanical requirements. The segments had to be lightweight (10-15 kg/m2), have high specific stiffness and be thermally stable. The segments had to have sufficient robustness for practical transport and use and be compatible with high-reflectivity coatings. ITT has designed a replicated, lightweight glass mirror solution to these manufacturing problems. This technology can be used to fabricate segments for CCAT. It can be used to fabricate segments for visible wavelength segmented telescopes or any other application requiring lightweight optics in large quantities. This technology enables the fabrication of large, lightweight mirror segments in a few weeks to a couple of months, depending on the figure requirements. This paper discusses the design of these mirrors and presents demonstrated results to date, including a 0.5 m diameter, 8 kg/m2 borosilicate mirror blank and 0.2 m diameter replicated borosilicate mirrors.