Glossary of Karst and Cave Terms
Based on "A Lexicon of Cave and Karst Terminology with Special to Environmental Karst Hydrology" EPA/600/R-02/003, 2002, EPA: Washington, DC., Speleogenesis Glossary includes 2699 cave & karst terms
A small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate, normally having a warty or knobby surface and no internal structure, and usually exhibiting a contrasting composition from the enclosing sediment or rock matrix in which it is embedded (e.g. a chert nodule in limestone.) Most nodules appear to be secondary structures in sedimentary rocks they are primarily the result of post depositional replacement of the rock and are commonly elongated parallel to the bedding. Nodules can be separated as discrete masses from the host material .