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 ?
Likewise, the limit line of the Clear Creek Chert (Fig.
Additionally, we expect that the eroded limit of the Clear Creek Chert (Fig.
In the Panhandle of Texas, chert replacement of the Alibates Dolomite (Guadalupian-Ochoan) has produced spherules (less than 5.
More than 12,000 years ago, local natives started to quarry chert from a small Alibates-capped hill within the Canadian River Valley, and tribes continued to quarry the colorful chert for weapons and tools into historic time.
He presented three hypotheses, including a replacement theory, for the genesis of the chert but did not find evidence to support any of them.
The primary objectives of this study were to determine the petrography of the chert and chert/dolomite contact zones, and interpret the probable origin of the chert.
Although no evaporite minerals were found in the dolomite or chert during this study, the Alibates does contain anhydrite and gypsum outside the study area.
The opal is similar in appearance to chert in the Alibates.
The Alibates is best known for its chert because of the ancient flint quarries, and yet the chert accounts for probably no more than two or three percent of the total exposure of Alibates.
The object of the analyses was to determine if any unusual elements or elemental relationships exist in the dolomite and chert.
0 metres of re-mobilized magmatic and sedimentary massive sulfides intercalated with sulphidic sediments and chert.
The hole was drilled north to south and intersected approximately 30 metres of sulphidic sediments and chert within ultramafics.