The word drusy, spelled with an s and pronounced with a z, is a mineralogical term that is used as both a noun and an adjective. The noun refers to mineral cavities which are lined (usually in quartz) with thin layers of tiny, tightly-packed crystals that resemble sugar granules. Each of these toppings are of a different fineness ranging from coarse to powdery. The mineral crust may also be found where it grew externally over another previously formed mineral. The adjective refers to any such granulated crystal layers.