a. The filling of desiccation cracks in mud, customarily in sandstone;
generally preserved as raised ridges (casts) arranged in polygonal
patterns on the underside of a sandstone bed. Pettijohn, 1
b. An irregular fracture in a crudely polygonal pattern, formed by the
shrinkage of clay, silt, or mud, generally in the course of drying.
Syn: sun crack; mud cast; shrinkage crack; desiccation crack.
Dictionary of Mining, Mineral, and Related Terms