Obsidian
Obsidian -
Called the Mirror Stone it reflects ones personal shortcomings such that they can come to the conscious to be dealt with, then let go of.
The most well know of the different colors is Apache Tears a black obsidian.
Obsidian can help protect against the negativity of others and has a grounding influence helping one to stay focused in the moment.
It can also help to stimulate analytical capabilities and precision, and can help promote a forgiving attitude and release of grievances.