A variety of silica that contains microcrystalline quartz.(noun)
A siliceous rock of chalcedonic or opaline silica occurring in limestone.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "chert" in a sentence
"The Lake Superior iron formations now consist near the surface mainly of interbanded quartz (or chert) and hematite, called _jasper_ or _ferruginous chert_ or _taconite_."
"Chert is sometimes called hornstone; also the term chert is often applied to any impure flinty rock, including jaspers."
"And why I have begun this column with what seems like a chain of free association is something that will probably become only marginally clear to you when I tell you that it was triggered by the news, last year, of the discovery at the Natural History Museum in London of the oldest known insect fossil, embedded in a chunk of a crystalline rock from Rhynie, S.otland known as chert -- a fossil that dates from the very same S.lurian period, four hundred million years back, that saw the flourishing of the eurypterids that T.S. Eliot's "ragged claws" line unaccountably calls to my mind."