Clast

Part of speech: noun

Pronunciation: /klæst/

Definitions

1. A fragment of rock resulting from the breakage of larger geological formations
2. A small particle or piece that has been separated from its original rock matrix through processes of erosion or weathering
3. Referring to any small, broken part of a larger solid that is typically found in sedimentary deposits

Etymology: "Clast" is a back-formation from "clastic," meaning that English speakers created the noun by stripping the ending off the adjective rather than building it up from a root. The adjective "clastic" came first, used in geology for rocks made of fragments of older rocks, and "clast" was then cut from it to name one of those pieces. The adjective itself is built from the Greek "klastos," meaning "broken," from the verb "klan," "to break." That same Greek root shows up in English words such as "iconoclast," literally a breaker of images, and "bronchoclast" and similar technical terms. So a rock fragment in geology is, at root, a broken piece, and the word's whole history is in that old Greek idea.

Synonyms: fragment, particle