Obsidian is a silica-rich volcanic rock which helps to connect the base or root chakra with the sacral chakra. If you are needing grounding during meditation, this is the perfect crystal. It is also known as the stone of strength and will help build your strength in times of need.
Obsidian will help deflect negative energy and psychic attacks. It is also the stone of reflection and can help you analyze the areas in your life that need attention.