We describe a process for fabricating light weight mirrors from single crystal silicon. The process uses conventional fabrication techniques in an unconventional sequence. The optical surface is ground and polished before light weighting. Distortion is minimized due to the crystalline nature of the material. A final trim polishing step creates no significant print-through due to the small amount of material removed. We are presently completing a set of 4" (10.2cm) diameter test mirrors good to better than 1/10th wave P-V (@633nm) or 1/80th wave RMS. Each mirror is a monolithic structure of single crystal silicon weighing about 80 grams. We are just starting a set of mirrors for the GeoSpec (Geostationary Spectrograph) instrument, including a 10" (25.4cm) diameter, F/3.5 primary.