A white, pale yellow, or colourless mineraloid consisting of fused silica that solidifies at temperatures above 1750 °C. It forms through meteorite impact, volcanism, and lightning strikes and occurs in association with shocked quartz, volcanic rocks, and sandy soil. Hardness 6.5, sp. gr. 2.5–2.7, lustre vitreous, cleavage absent, fracture conchoidal, streak white.