If one of your crystal glasses becomes chipped, you do not necessarily have to throw out the glass. You can repair the chip in the glass and make it as close to new as possible. There are epoxies and other types of cement you can use to glue pieces of glass back together, even small chips in the surface. Make sure you use an epoxy substance specifically designed for repairing drinking glasses.
Wash and wipe the chipped areas on the glass using a wet cloth to clear any dirt off the chip and reduce the friction on the glass. Do the same with the chip itself, holding it with tweezers if needed.
Sand down the surfaces of the chip and the glass to smooth them out, wrapping sandpaper around a pencil or similar small dowel/rod. It's best to sand the entire area with coarse sandpaper and repeat twice with medium and then fine sandpaper.
Wipe off the glass and the chip with the wet cloth one more time.
Spread newspapers around your work area and mix up a glass epoxy, following the specific instructions included with your particular epoxy brand.
Apply the epoxy to the surfaces of both the chip and the glass surface using a small brush or any other tool the epoxy instructions recommend.
Press the chipped glass piece back into the chipped hole in the glass itself using the tweezers, and then tape over the glass surface with clear or masking tape. Wait for the epoxy to cure and harden, according to the time given in the instructions, then remove the tape.