chert

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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 ?
Andesitic, tuffaceous sedimentary rocks flanking and above massive ore bodies locally contained abundant disseminated pyrite as well as anhydrite, barite and cherty zones (Payne et al.
Hydroxylapatite in matted fibers constitutes the principal component of dirty gray, dense, cherty looking crusts up to 1 cm thick separating yellow crandallite layers from the variscite cores.
In the short run, lost income is only partly offset by unemployment insurance (UI), making it difficult for some households to manage their financial obligations during spells of unemployment (Gruber, 1997; and Cherty, 2008).
The surface of these plains is dotted by numerous mesas and buttes, which formed of early Eocene limestone with cherty bands.
Empirical studies of cross-country differences in employment rates suggest that high unemployment benefit replacement rates tend to significantly reduce employment rates (Bassanini and Duval, 2006), while microeconometric evidence for other countries suggests that labour supply is very sensitive to high participation tax rates (Blau and Kahn, 2007; Blundell and Macurdy, 1999; Cherty, 2009; Eissa and Hoynes, 2006; Gruber and Saez, 2002; Immervoll et al.
The bedrock of FODO is of upper Mississippian age composed of various slowly soluble cherty limestones (United States Department of Agriculture, 1953).
Program Directors Raj Cherty, University of California, Berkeley, and Amy Finkelstein, MIT, organized the meeting.
5 million bf of kiln-dried lumber in 13 different species: alder, basswood, beech, birch, cherty, hard maple, hickory, poplar, red oak, soft maple, walnut, white ash and white oak.
Figure 1 presents the number of dividend initiations by quarter for the constant number of firms sample that Cherty and Saez (2005) use to document that a surge in dividend initiations occurred in the third quarter of 2003, immediately following the tax reduction.
deals don't have to be (minimum guarantee deals), they can be P&A deals; and we can use all the variants on the independent finance model -presales, gap, mezzanine and equity," Cherty says.
18) See, eg, R v Cherty (1803) 2 East PC 556; R v Bloxham (1944) 29 Cr App R 37; R v Davies [1970] VR 27, 29 (Gowans J for Winneke CJ, Gowans and Newton JJ).