Chert

[tʃә:t]

(noun.) variety of silica containing microcrystalline quartz.

Typed by Edwina--From WordNet

(n.) An impure, massive, flintlike quartz or hornstone, of a dull color.

Edited by Arnold

n. a kind of quartz or flint: hornstone.—adj. Chert′y like or containing chert.

Typist: Wanda