What describes a crystal growth habit characterized by a bumpy appearance?

The term that describes a crystal growth habit characterized by a bumpy appearance is "Botryoidal." This term is derived from the Greek word "botryon," which means "bunch of grapes," reflecting the rounded, globular shapes that form during the crystal growth process. Botryoidal formations typically exhibit a smooth, rounded surface that gives a bumpy or lumpy texture, commonly seen in minerals such as malachite, hematite, and chalcedony.

Boulder opal refers specifically to a type of opal found in ironstone, which can display patterns of color and is not defined by a bumpy growth habit. Cabochon refers to a style of gem-cutting, typically involving a smooth, rounded surface rather than a bumpy texture. Calcareous concretion refers to a rock formation that contains calcium carbonate; while it can also exhibit a specific shape or texture, it does not specifically denote a bumpy appearance linked to crystal growth. Thus, among the options, "Botryoidal" is the only term that accurately describes the bumpy growth habit.