Obsidian is volcanic lava that has been cooled quickly. It is a natural glass and a stone which is known for its protective qualities. As such, it was probably one the first stones to be used for arrowheads and knives.
Among the ancient Aztecs, Obsidian was sacred to the Sky God Tezcatlipoca. The Aztecs also fashioned it into mirrors which the scryers used in divination. Obsidian was also used for eyes in idols in the Temple of Quetzalcoatl. Obsidian was also popular among certain North American Indians.
Obsidian comes in many forms, from black obsidian to snowflake and even rainbow. Each type will have slight variations on healing.
It is a very protective stone, and is excellent for removing negativity. It is also excellent protection against psychic attacks. It is a very grounding stone and very healing. Obsidian will help you to focus your thoughts.
Physically it benefits the stomach, intestines, muscle tissue, and can rid one of bacterial or viral infections. It sharpens and focuses internal and external vision, and helps get in touch with buried issues before they explode.
Obsidian is related to the root chakra. It will help to ground your energies.
Astrological: Stone of Scorpio.