chert and flint
Very fine-grained quartz, a silica mineral with minor impurities.Flint is gray to black and nearly opaque (translucent brown in thin splinters). Opaque, dull, whitish to pale brown or gray specimens are called simply chert. Chert and flint provided the main source of tools and weapons for Stone Age people. Flint is used today as an abrasive agent on sandpapers and in mills that grind raw materials for the ceramic and paint industries. Considerable amounts of chert are also used in road construction and as concrete aggregate. Some chert takes an excellent polish and is used as semiprecious jewelry. See also siliceous rock.
* * *▪ mineralvery fine-grained quartz (q.v.), a silica mineral with minor impurities. Several varieties are included under the general term chert: jasper, chalcedony, agate (qq.v.), flint, porcelanite, and novaculite.Flint is gray to black and nearly opaque (translucent brown in thin splinters) because of included carbonaceous matter. Opaque, dull, whitish to pale-brown or gray specimens are simply called chert; the light colour and opacity are caused by abundant, extremely minute inclusions of water or air. The physical properties are those of quartz (see silica mineral [table]).Chert and flint provided the main source of tools and weapons for Stone Age man. The uniform fine grain, brittleness, and conchoidal fracture made it relatively easy to shape arrowheads by flaking off chips, and the edges produced were quite sharp. Quarrying and manufacture of flint weapons were among humankind's earliest business ventures, and it is sometimes possible to trace ancient trade routes by knowing where a particular type of flint was obtained. From the 17th through the early 19th century, flints again found extensive military use in flintlock rifles. Crushed flint is still used as the abrasive agent on sandpapers for the finishing of wood and leather. In addition, flint pebbles are used in mills that grind raw materials for the ceramic and paint industries; the use of flint pebbles instead of steel balls as a grinding agent is desirable in order to avoid contaminating the product with iron. Considerable amounts of chert are also used in road construction and as concrete aggregate. Some chert takes an excellent polish and serves as semiprecious jewelry.Chert and flint occur as individual nodules or layers of nodules in limestone or dolomite; they are common in rocks of all ages (notably in the Cretaceous chalk of England). Hard and chemically resistant, the nodules become concentrated in residual soils as the surrounding carbonate rock weathers away. In places, chert forms massive beds several hundred metres thick with a lateral extent of hundreds of kilometres. Chert also occurs as a fine powder disseminated throughout carbonate rock; it impregnates shale and, rarely, forms cement in sandstone. It also develops in the vicinity of some metalliferous veins, precipitated by hot ore-depositing (hydrothermal) solutions. Erosion of chert beds or chert-bearing limestone produces chert pebbles, which are abundant in river and beach gravel.Most chert and flint has formed by replacement of the enclosing carbonate sediment after burial beneath the seafloor. This replacement origin (similar to the petrification of wood) is substantiated by preservation in chert of the minute textural details of the enclosing carbonate rocks.Bedded chert, also referred to as ribbon chert, is made up of layers of chert interbedded with thin layers of shale. Many bedded cherts are made up of the remains of siliceous organisms such as diatoms, radiolarians, or sponge spicules.
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Chert — For the Spanish municipality, see Xert. Chert Chert ( / … Wikipedia
chert — [chʉrt] n. [< ?] an extremely dense type of quartz, including jasper and flint, having a dull, opaque luster and made up of microscopic crystals cherty [chʉrtē] adj. chertier, chertiest … English World dictionary
Flint tool — Chipped stone tools were made by stone age peoples worldwide. Paleolithic tools were relatively simple, repeated small flakes being struck or pressed from a cobble or nucleus until the required shape was achieved. This is called knapping. Freshly … Wikipedia
Flint — (or flintstone) is a hard, sedimentary cryptocrystalline form of the mineral quartz, [ [http://webmineral.com/data/Quartz.shtml General Quartz Information] Webmineral.com (page contains java applets depicting 3d molecular structure)] [… … Wikipedia
flint — /flɪnt / (say flint) noun 1. a variety of chert, resembling chalcedony but more opaque, less pure and less lustrous, and producing conchoidal fractures. 2. a piece of this, especially as used for striking fire. 3. something very hard or obdurate … Australian English dictionary
flint — [flint] n. [ME < OE, akin to Norw, stone splinter: see FLINDERS] 1. a dark colored variety of chert that produces sparks when struck with steel and that breaks into pieces with sharp cutting edges 2. a piece of this stone, used to start a fire … English World dictionary
Flint Hills — The Flint Hills, historically known as Bluestem Pastures or Blue Stem Hills [GNIS|480069|Flint Hills] , are a band of hills in eastern Kansas stretching into north central Oklahoma, extending from Marshall County in the north to Cowley County,… … Wikipedia
chert — noun a) Massive generally dull colored and usually opaque quartzite or hornstone or impure chalcedony or other flint like mineral. By general usage in mineralogy and geology, a chert does not have a conchoidal fracture. In North American… … Wiktionary
flint — A concretionary form of silica, similar to chert, that occurs in chalk as tabular sheets and layers of irregularly shaped nodules. Being very hard and relatively insoluble, flint tends to stand out from chalk cliffs. Flint rich horizons may… … Lexicon of Cave and Karst Terminology
flint — noun a hard grey rock consisting of nearly pure silica (chert), occurring chiefly as nodules in chalk. ↘a piece of flint shaped to form a primitive tool or weapon. ↘a piece of flint used with steel to produce an igniting spark. Origin OE; related … English new terms dictionary