We don't find many quartz drusy/crystal clusters that have this much smokiness to them. It happens when there are other minerals in the soil and rock which colour the quartz. I am not sure which minerals but I would guess iron oxides. Temperature and other environmental factors also create this smokiness.
 
This crystal came from the southern hills of Scotland, found by the Stone Circle team on one of our many rockhounding adventures. It has cool smoky quartz crystals that would have been clear without any other minerals being present. Follow us on TikTok to see us finding this sort of material.