Glitterdust is the powdered form of a rock found along the Wounded Coast. When explorers brought the sparkling rock to the markets of the Free Marches, it became immediately popular among wealthy ladies who crushed it and applied the powder to their faces. The added brightness and lustre to the skin, however, soon paled in comparison to the developing rash and coughing fits.
As it turned out, glitterdust is dangerous if ingested or inhaled. It's also extremely flammable, as several ladies discovered after powdering their hair while standing next to a candle. Unfortunately, this resulted in a dozen deaths by conflagration.
These days, glitterdust is used sparingly, and only by experienced alchemists. The most common form of the substance is Volatile Glitterdust. If gathered from caves where darkspawn dwell, the rock produces a powder known as Tainted Glitterdust.
—An excerpt from The Alchemist's Encyclopedia, by Lord Cerastes of Marnas Pell