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 back at the start, maybe 2022. It has cool smoky quartz crystals blanketing a flat face with some oddly shaped crystals on one end. They may be calcite or massive quartz.

Above these and right on the end of the rock, the druzy continues with the addition of a few bigger crystals leaning towards cluster size.