Obsidian is a naturally occurring volcanic glass that is formed when lava cools quickly with minimal crystal growth. It comes in a variety of colors such as black, brown, and mahogany, and has been used for thousands of years for weapons, tools, and decorative items. In crystal healing, obsidian is believed to help with grounding and protection, as well as aiding in releasing negative energy and promoting emotional healing. It is also believed to have a strong connection with the root chakra.