A variety of Quartz crystal ranging in color from light to dark brown to black. Also called Cairngorm Stone or Morion - I tend to reserve the latter name for the nearly black variety. You can often get a Smoky Citrine shade which I find more mellow. Smoky Quartz is a base chakra stone. It awakens your physical cellular consciousness. There's a good example from my own experience, For a long period  I'd been working long intense hours and suffering migraines. Working with Smoky, I kept falling asleep !  Finally I realised that's just what my body needed.  My physical cells had gained consciousness and spoken. I've not had a migraine since. I've learned to rest up when needed.