encrustations

Encrustation is the development of a crust-like layer on a surface as a result of deposition of minerals or growth of organisms. Encrustations can be inorganic, formed by mineral precipitation, or organic, produced by sessile organisms such as algae, bryozoans, or sponges. They may occur on rocks, shells, corals, sediment grains, or man-made structures exposed to water or soil.

Mineral encrustations form when minerals dissolved in water reach supersaturation and precipitate onto a surface, often creating continuous crusts or sparry coatings. Biological encrustations arise when organisms attach and grow, sometimes cementing a continuous layer; microbes can also mediate mineral precipitation, shaping the texture and composition of the crust.

Common settings include marine environments where encrusting coralline algae and bryozoans coat shells and rocks; freshwater and terrestrial settings produce iron-oxide crusts, calcareous coatings, or crusts on cave surfaces. Encrustations also occur on ship hulls, pipelines, and other submerged infrastructure as biofouling or mineral deposition.

Encrustations record environmental conditions and biological communities, aiding palaeoenvironmental reconstructions. They can create microhabitats and influence surface properties, such as roughness, adhesion, and corrosion resistance, with practical implications for engineering and conservation. In archaeology and paleontology, preserved encrustations provide clues to past ecosystems and diagenetic processes.

The term is used in several disciplines, including geology, marine biology, dentistry, and industrial engineering, with context clarifying whether it refers to mineral crusts or biological coverings.