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 ?
Number, movements, and general biology of Steller sea lions on Tuleny Island [Chislennost', peremeshcheniya i osnovnye cherty biologii sivucha o.
Jones (1953) and Wilson and Majewske (1960) recognized four subdivisions of the "cherty Lower Devonian" in the subsurface of the Midland Basin, in ascending order: (1) dark shale with conodonts and spores (0-45 feet thick); (2) dark chert and cherty limestone (100-300 feet thick); (3) fossiliferous calcarenitic limestone (450 feet thick); and (4) light-colored chert and limestone (200 feet thick).
Species: Red oak, maple, white birch, cherty, European beech, alder, knotty alder, knotty pine, birch, walnut, mahogany, pecan, MDF
An interval of cherty rocks having alternating silica-rich and silica-poor layers, situated at the stratigraphic contact between the footwall mafic volcanic and hangingwall sedimentary successions, likely reflects a chemical precipitate deposited during a hiatus in volcanic activity prior to the onset of turbidite sedimentation (Fig.
John Do cherty, Loan head, said: ''Ricks en's forearm smash was 10 times worse than what Harts on was supposed to have done.
Large points are found throughout the Kimberley, but it is only in the south and southeast that craftsmen, utilising massive white cherty material suitable for heat treatment, consistently produced points more than 80 mm long.
In particular a cherty horizon, analyses tabulated above, that caps known sulphide mineralisation displays abundant indications of a strong VMS system (high Cu, Zn, Pb, Au, Ag, low Mg, Ti, Al).
Several zones of stratiform sulfide replacement mineralization with cherty silica alteration containing up to 70% sulfides, primarily fine-grained pyrite, arsenopyrite and stibnite and to a lessor extent chalcopyrite and sphalerite, have been located within the claim group.
Species: Alder, ash, birch, cherty, mahogany, hard & soft maple, red oak, poplar, walnut, MDF, others on request
Tadashi Fukui, Kyoto Sangyo University, and Yasushi Iwamoto, University of Tokyo, "Policy Options for Financing the Future Medical and Long-Term Care Costs in Japan" Discussants: Epictetus Patalinghug and Raj Cherty
Overlying, and in thrust fault contact with, the Rabbitkettle Formation are black shales and black cherty siltstones of the Earn Group (Portrait Lake Formation).
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