chert


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Related to chert: Dolostone, micrite

chert:

see flintflint,
variety of quartz that commonly occurs in rounded nodules and whose crystal structure is not visible to the naked eye. Flint is dark gray, smoky brown, or black in color; pale gray flint is called chert.
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Chert

 

a mineral formation consisting of crystalline and amorphous silica (opal, chalcedony, or quartz). Chert is widespread in nature in the form of concretions, nodules, and seams that either lie parallel with the enclosing limestone and chalk deposits or cut across bedding. It is formed either by diagenesis of deposits, by catagenesis of rocks, or by weathering. It has a hardness of 7 on the mineralogical scale and breaks with a conchoidal fracture. Because of its ability to form a sharp cutting edge when chipped, chert (flint) was used by man from the most ancient times to the Iron Age to make stone tools.

chert

[chərt]
(petrology)
A hard, dense, sedimentary rock composed of fine-grained silica, characterized by a semivitreous to dull luster and a splintery to conchoidal fracture; commonly gray, black, reddish brown, or green. Also known as hornstone; phthanite.

chert

A very fine-grained dense rock consisting of chalcedony or opal, often with some quartz, and sometimes with calcite, iron oxide, organic matter, or other impurities; has a homogeneous texture and white, gray, or black color; some of its constituents may react with cement alkalies and therefore may be undesirable as concrete aggregate for exposed concrete in northern climates.
References in periodicals archive ?
Additionally, we expect that the eroded limit of the Clear Creek Chert (Fig.
Petrofacies (P4): presenta cemento calcareo en un 24%, contenido considerable de plagioclasa y liticos metamorficos (filitas micaceas), sedimentarios (lodolitas y limolitas), ausencia de liticos volcanicos como tambien presencia de intraclastos siliciclasticos, cuarzo policristalino foliado, chert, feldespato y micas.
Stratigraphic unit 2 (5-27 cm depth) is more compact than unit 1, and is comprised of a fine grey, sandy silt that contains chert artefacts, faunal remains, and freshwater mussel shell.
Large primary flakes with cortex indicate that unprocessed Ramah chert was transported to site locations.
There is a heavy emphasis on the use of quartz and rhyolite in the debitage, compared to an emphasis on chert and rhyolite for formal tools (Table 6).
Period Group Formation Lithology Aquifer potential Lower Balqa Umm Rijam Chert, Semi aquifer Tertiary (B4) limestone Muwaqqar Chalk, Aquitard (B3) Marl Al Hasa Phosphate Good (B2a) aquifer Amman Silicified Aquifer (B2b) Limestone interrupted Wadi Ghudran Chalk, aquiclude (Bl) Chalky marl Cretaceous Ajlun Wadi As Sir Limestone good aquifer (A7) Shueib Marly Aquitard to badly (A5-6) Limestone developed aquifer Hummar Dolomitic Semi aquifer (A4) Limestone Fuhais Marl Aquitard, partly (A3) semi aquifer Na'ur Marly Semi aquifer (Al-2) Limestone Period Group Thickness (meter) Lower Balqa 70 m Tertiary 60-70 m 60 m 50 m 20 m Cretaceous Ajlun 20 m No outcrop No outcrop No outcrop No outcrop Table 2.
La composicion de las particulas en la capa inferior del segmento es de chert (80%), litoarenitas de grano fino (20%) y en menor proporcion vulcanitas (<5%), en las capas superiores de este segmento se observa un cambio en el predominio de la composicion de los clastos, pasando a contenidos de chert (40%) y mayor presencia de clastos de litoarenitas (70%).
The two ball chert zones in the middle Fredonia occur in a lithographic to finely crystalline limestone interval; white to gray color and includes spirifer brachiopods, horn corals, and the rugose coral (Lithostrotion harmodites).
Keywords: obsidian, New Britain, chert, stemmed tools, mid-Holocene, sources
Although we couldn't swear to have seen any flakes of chert in the cuttings, if there were layers of flint nodules, they would certainly slow the drilling.
The claim that the Apex Chert formation was carbon-based life forms has always been controversial, and so geologists from the University of Kansas decided to take another look.
9:45 CHERT HUNTING: MODELING PREHISTORIC LITHIC RESOURCE RANGES IN