If you are looking for a grounding stone Black Obsidian is a nice choice.  It shields against negativity and increases and stimulates the gift of prophecy.  It is excellent for healing and cleaning out the psyche of negative thoughts and experiences that one has accumulated during course of the day.  

It helps to release one from resentment of others, fear and anger.  It is very grounding, very healing and is also an excellent Stone of Manifestation.  Try creating a grounding grid and use a Black Obsidian wand for activating the crystals energies or incorporate black obsidian rough, polished or tumbled pieces.

These are highly polished and reflective chips (1 ounce) that come with a drawstring pouch and a crystal description card.

The selenite bowl (available separately) and the shell are for display purposes.