Quartz, SiO2 Druzy variety. The term druzy describes coatings of fine, or small mineral crystals on a base rock, and can be applied to crystals of all minerals. This 22Kg. specimen was collected on the shore line of the Nant y moch reservoir in west Wales, immediately adjacent to the Bryn y rafr mine. The crystals cover about 60% of the host rock, and are mostly white, but with some iron staining.