How to Repair Quartz Countertops
To repair a small chip or crack in your quartz countertop, try a hard, 2-part, clear epoxy (available from Home Depot or Lowes, or online here).
Polish it down using very fine sandpaper, followed by a polishing compound. Epoxies can be tinted, which is nice.
NOTE: Make sure you leave just the required amount of epoxy on the surface to dry, as rubbing it down will take a long time; it’s more difficult to get rid of the excess once it dries.
If you’d be more comfortable using a system that’s intended just for the purpose of repairing engineered stone surfaces, for $499, you can buy the Dani Designs E-Stone Scratch repair kit. It comes with everything you need to repair your countertop, including 40,20,&10 micron diamond discs and a training DVD.