An encrustation or deposit of hard, calcareous cement made up of nitrates, sulfates, halides, and sand. It appears on the surface of materials such as bone, ceramic, or stone after they have been buried or exposed to moisture for an extended time. These layers of calcium carbonate (lime accumulation) are often present in semiarid or arid areas, either on top of or within the soil - as in the desert basins of southern Arizona.