An encrustation is a hard layer or crust that forms on the surface of something, usually built up over time. When a ship sits in the ocean for years, barnacles and other sea creatures attach themselves to its hull, creating a thick encrustation that must be scraped off. When minerals in water slowly deposit on the inside of old pipes, they form an encrustation that can eventually clog the flow.

You might see encrustation on ancient coins dug up from the ground, where dirt and minerals have hardened into a layer that hides the original metal. Jewelers sometimes create encrusted decorations by covering objects with gems or crystals: a crown encrusted with diamonds has jewels packed closely together across its surface.

In nature, encrustation happens constantly. Coral reefs grow through encrustation as tiny animals build their hard skeletons on top of older ones, layer after layer. Caves develop encrustations of sparkling minerals that drip down and harden over thousands of years. The process is usually slow but relentless, turning smooth surfaces rough and adding weight and texture where none existed before.