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Chert varies greatly in color, from white to black, but is most often found as gray, brown, grayish brown and light green to rusty red [9] [10] and occasionally as dark green. [11] Its color is an expression of trace elements present in the rock. Both red and green are most often related to traces of iron in its oxidized and reduced forms ...
Flint occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. [3] [4] Inside the nodule, flint is usually dark grey or black, green, white, or brown in colour, and has a glassy or waxy appearance. A thin, oxidised layer on the outside of the nodules is usually different in colour, typically white and rough in ...
In geology and particularly in sedimentology, a nodule is a small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition from the enclosing sediment or sedimentary rock. Examples include pyrite nodules in coal, a chert nodule in limestone, or a phosphorite nodule in marine shale.
For example, concretions in sandstones or shales are commonly formed of a carbonate mineral such as calcite; those in limestones are commonly an amorphous or microcrystalline form of silica such as chert, flint, or jasper; while those in black shale may be composed of pyrite. [18]
The Corriganville Limestone was first described by J. W. Head in 1972 as part of the Helderberg Group in Allegany County, Maryland, as a gray limestone with chert. [11] C. R. Wood first mapped it as part of the Old Port Formation in Pennsylvania. [12] The type locality is a railroad cut 0.3 mi southeast of Corriganville, Alleghany County ...
Mapped as 1 unit. Tin Mountain Limestone 1,000 feet (300 m) thick, is black with thin-bedded lower member and thick-bedded upper member. Unnamed limestone formation, 725 feet (221 m) thick, consists of interbedded chert and limestone in thin beds and in about equal proportions. Mixed brachiopods, corals, and crinoid stems.
Chert is a siliceous (silica) stone, a variety of quartz similar to flint but more brittle. It naturally occurs as large, flat, elliptically shaped nodules in creek beds, and sometimes as hill-top residuum. The nodules were formed as part of the Ullin limestone formation during the Mississippian geologic period (roughly 359 to 318 million years ...
Knapping is the shaping of flint, chert, obsidian, or other conchoidal fracturing stone through the process of lithic reduction to manufacture stone tools, strikers for flintlock firearms, or to produce flat-faced stones for building or facing walls, and flushwork decoration.