Obsidian changes to gneiss under high-grade metamorphic forces. Obsidian is formed from quickly cooled lava, which is the parent material. Extrusive formation of obsidian may occur when felsic lava cools rapidly at the edges of a felsic lava flow or volcanic dome, or when lava cools during sudden contact with water or air. Obsidian is volcanic glass that forms naturally. It comes from the rapid cooling of felsic lava. Obsidian is naturally black in color and has a glassy texture and a vitreous luster. Wind and water can break igneous rock into sediments.