Obsidian is a naturally occurring volcanic glass formed when lava cools rapidly without crystallising. It is typically found in areas with volcanic activity, such as Iceland, the western United States, and parts of the Andes, but it has been traded and used around the world for thousands of years. Physically, obsidian is hard and brittle, with a smooth, glassy texture and a sharp, conchoidal fracture, meaning it breaks with curved, shell-like edges. It is usually black, but can also appear in shades of brown, green, or even have a sheen or “snowflake” pattern due to mineral inclusions.