Obsidian

Obsidian is a natural volcanic glass, formed by the very rapid cooling of silica-rich lava, which prevents the formation of crystals. Composed mainly of silicon dioxide (SiO₂), it generally has a black color, but can also be brown, gray, green, or multicolored.

Its varieties include black, mahogany, snowflake, golden, rainbow, and celestial eye obsidian. It is characterized by its vitreous luster, smooth texture, and conchoidal fracture.