Obsidian is a great protective stone especially against Psychic attacks. Obsidian is known for removing negativity. Obsidian protects the gentle from abuse, and is used to cut attachment cords. It is a very grounding stone with nice healing properties.
We use Blue Obsidian in our Chakra stone kits. We use it with the 5th, or Throat Chakra. This chakra is associated with Creativity and self expression, and is located at the Throat. Blue is the associated color with the fifth Chakra.