What does chert mean?
Chert is a hard, dense, fine-grained sedimentary rock made up almost entirely of microcrystalline quartz. It typically forms as rounded nodules embedded within limestone or chalk — the way flint does in English chalk formations — or as distinct layered beds deposited from silica-rich waters. Because it breaks with a sharp conchoidal fracture and is extremely durable, chert was one of humanity's most important raw materials before metals: prehistoric peoples across the world knapped it into arrowheads, scrapers, and cutting tools. In modern usage the word belongs mainly to geology and archaeology, where it denotes both the rock itself and the worked artefacts made from it. It carries no figurative or emotional connotations; its value lies in precision. Related terms include flint (a particular variety found in chalk) and hornstone. For anyone reading about ancient toolmaking, sedimentary sequences, or landscape formation, chert is a word worth recognising on sight.
nounA hard, dense, fine-grained sedimentary rock composed chiefly of microcrystalline quartz, occurring as nodules or layered beds, especially in limestone and chalk.
- A hard, dense, fine-grained sedimentary rock of microcrystalline quartz, occurring as nodules or layers, especially in limestone and chalk.
"The cliffs along the coast are riddled with nodules of chert weathering out of the chalk."
"The archaeologists recovered chert flakes from the prehistoric campsite."
"Bedded chert layers in the marine sequence record ancient silica-rich conditions on the seafloor."
Used mainly in geological writing when referring to multiple varieties, occurrences, or samples of the rock.
"The formation contains several distinct cherts of differing colour and texture."
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chert
The origin of 'chert' is uncertain; it appears to be of local or dialectal English origin, first recorded around the early seventeenth century, though its precise source remains obscure. It has no widely accepted cognates in other languages, and attempts to link it to older roots have not produced consensus among etymologists.
Related word forms
How chert is actually used
Primarily used in geology, mineralogy, and archaeology; a technical term rather than everyday vocabulary. Often used interchangeably with flint in casual speech, though specialists distinguish them.
Easily confused with chert
Flint is a specific variety of chert that occurs in chalk deposits; chert is the broader rock type.