A natural volcanic glass, obsidian is formed by the rapid cooling of volcanic magma. Typically jet black, this igneous rock comes in many varieties such as mahogany, snowflake, sheen, spider web and rainbow. Obsidian’s conchoidal fracture makes it easily chipped to form razor-sharp edges. It was used by many ancient cultures to make weapons, tools, and ornaments. Metaphysically, obsidian is used for protection and the release of negative energy. Locations include Oregon, Mexico, Japan and Iceland.