Black Quartz is called "Black" quartz because it often has black inclusions, although clear examples exist too, and are said -- and in my experience do -- have the same energetic vibration.
Black Quartz is a powerful stone with purifying energies and the vibration of the "OM". It can be used for balancing all chakras and meridians. It can also be used for very powerful energy grids and deep spiritual meditation.
Black Quartz is also excellent for dissolving energy blockages and purifying energies. This makes it superb for protection of the aura or an environment and will also purify the aura or environment. It is often used in the corners of a room for purifying energies and protecting the space from negative energies. Wearing or carrying this type of quartz will cleanse the aura and protect it from negative influences, as well as helping ground the wearer.
Physically, Black Quartz is used in crystal healing for powerful healing of any type, removal of toxins and other impurities, and moving illness energies out of the body. Note that healing crystal meanings are spiritual supports to healing and are not prescriptions or healthcare information.