Obsidian  
Chakra: Base
Brings wisdom and offers protection. Good for learning. Good for the colon. Helps gastroenteritis, IBS, and nausea. Grounding. Helps self-defeating patterns and subconscious blockages. Acts as a mirror of the soul.
 
Onyx  
Chakra: Base
Good for decision making. Brings luck and happiness in the home. Good for bone marrow and feet. Helps grief and lack of self-control. Helps you take charge of situations. Good for yin/yang balance.