Any of a variety of chemical solutions used to polish silicon wafers using a CMP. Probably more accurately referred to as colloidal silica. According to this MSDS I'm looking at, Brand D Slurry, made by DuPont, consists of 30-40% amorpous silica, 0-0.5% titratable alkali (Na2O) and 60-70% water.

For more information, you can call DuPont at 1-800-441-7515.
In case of a medical emergency, call 1-800-441-3637. And then call 911.