Source: Ultimate Equipment, pg(s). 246
A medusa mask is a magical device made of gold-plated iron. It has a distinctly serpentine look, with writhing snake bodies the dominant feature. The eyes of the mask are made of dark, translucent crystal and give the wearer an increased ability to see through illusions and a defense against debilitating gazes. Once a day, the wearer can cause the eyes to glow with a pale green light and temporarily turn a nearby creature to stone.