chert

IPA: tʃˈɝt

(geology, uncountable) Massive, usually dull-colored and opaque, quartzite, hornstone, impure chalcedony, or other flint-like mineral.
(countable) A flint-like tool made from chert.

Examples of "chert" in Sentences

Chert is sometimes called hornstone; also the term chert is often applied to any impure flinty rock, including jaspers.
We don't use the kind of chert that we used to because we don't have the type of chert roads, but this will work out better because it will cut our costs down. "
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_.
When all you have is a knife (only carbon blades work; stainless is too hard), you may be able to get a spark by striking its back with a sharp stone chip, such as chert or flint.
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.