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An argillaceous sandstone characterized by an abundance of unstable mineral and rock fragments and a fine-grained clay matrix binding the larger, sand-size detrital fragments.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a rock of sedimentary origin consisting of small fragments (grains) of sedimentary and chiefly metamorphic and igneous rock with an admixture of fragments of basic volcanic rock and tufogenic material. A significant quantity of cementing material is characteristic. The color is usually dark gray, black, or dark green (owing to the chlorite in the cement). The fragmentary grains in the graywacke are angular or slightly rounded and are poorly sorted. Graywackes are typical for geosynclinal areas where they form thick strata originating during periods of the rapid accumulation of disintegration products from internal uplifts composed of more ancient rock.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
9 scales the spontaneous imbibition of water into different porous media (Berea, chalk, and Graywacke cores) with different initial water saturations.
9 and 18 successfully scaled their spontaneous imbibition water-air experiments in sandstone, chalk, and Graywacke rock samples.
The brewery found a quarry to supply graywacke stones, which could stand the temperatures involved, and the "stone" beer brewing process was reborn.
Identification [[gamma].sub.unsat] [kN/[m.sup.3]] quartenary cover 18 graywacke 22.65 claystones heavily mouldered 20.55 and lightly mouldered 22.7 sillstone undisturbed 24.3 Identification [[gamma].sub.sat] [mu] [kN/[m.sup.3]] [-] quartenary cover 21 0;35 graywacke 24.65 0.25 claystones heavily mouldered 22.55 025 and lightly mouldered 24.7 0.25 sillstone undisturbed 26.3 0.25 Identification [E.sub.ref] [c.sub.ref] [kN/[m.sup.2]] [kN/[m.sup.2]] quartenary cover 2000 10 graywacke 2000000 80 claystones heavily mouldered 1500000 20 and lightly mouldered 2000000 60 sillstone undisturbed 2S00000 SO Identification [phi] [*] quartenary cover 19 graywacke 42 claystones heavily mouldered 36 and lightly mouldered 38 sillstone undisturbed 42 Table 2 Parameters of record of blasting operation.