Obsidian is a very protective stone, and is excellent for removing negativity. It is also excellent protection against psychic attacks. In particular obsidian protects the gentle from abuse, and is used to cut attachment cords to release one. It is a very grounding stone, and very healing.
Obsidian is also an excellent manifestation stone.Note that healing crystal meanings are spiritual supports to healing and are not prescriptions or healthcare information. Obsidian is related primarily to the root chakra, though differing colors may relate to different chakras as well.