Also 7–8 chirt. [App. a local term, which has been taken into geological use. Origin not ascertained. Prof. Skeat compares Kentish place-names like Brasted Chart; but this chart is explained by Parish and Shaw as ‘a rough common overrun with gorse, broom, bracken, etc.,’ whence charty rough uncultivated (land).]
A variety of quartz, resembling flint, but more brittle, occurring in strata; also called hornstone. Also applied to various impure siliceous or calcareo-siliceous rocks, including the jaspers.
1679. Plot, Staffordsh. (1686), 124. A sort of black Chalk found between the beds of Chirts, and the beds of gray Marble.
1729. Martyn, in Phil. Trans., XXXVI. 30. Chert, this is a kind of Flint … called so, when it is found in thin Strata.
1734. Phil. Trans. (abridged), VI. II. 192. The Strata of Chert are often four Yards thick.
1747. Hooson, Miner’s Dict., E iv b. Attended with small Chirts, Cauks, etc. according to the Nature of the Vein.
1813. Bakewell, Introd. Geol. (1815), 211. Seams of siliceous earth, called chert, which nearly resembles flint.
1853. Lyell, Princ. Geol., Gloss. Chert, A gradual passage from chert to limestone is not uncommon.
1868. Dana, Min. (1880), 195.
2. attrib. and in comb.
1863. Reader, 14 Feb., 173/3. Flint and chert implements were found in much lower positions.
1865. Daily Tel., 3 Nov., 5/4. The ‘mill-room’ in which huge chertstones are shoved round by iron arms.
1888. J. Ward, in Jrnl. Derbysh. Archæol. Soc., X. 48. The skeleton lay upon a bed of chert-fragments.
