Smoky Quartz is used by healers to transmute negative and low vibes in a space or a persons auric field. It is believed to absorb the toxic frequencies to protect the user and occupants of a space. Smoky Quartz does need to be cleared with smudge smoke or a sound bath to keep it working well for you. 
Smoky Quartz is used to help support those doing heavy metal cleanses, holistic healing and chemo or radiation treatments as it is believed to help support the body move out toxins.