chert


noun

  1. a compact rock consisting essentially of microcrystalline quartz.

noun

  1. a microcrystalline form of silica usually occurring as bands or layers of pebbles in sedimentary rock. Formula: SiO 2 . Varieties include flint, lyddite (Lydian stone)Also called: hornstone
n.

“flint-like quartz,” 1670s, of unknown origin. Apparently “a local term, which has been taken into geological use” [OED].

  1. A hard, brittle sedimentary rock consisting of microcrystalline quartz. It is often reddish-brown to green but can also occur in a variety of other colors, especially white, pink, brown, or black. Chert often contains impurities such as calcium, iron-oxide, or the remains of silica-rich organisms. It usually occurs as nodules in limestone and dolomite and has curved fractures.

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