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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 It might be outdated or ideologically biased.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 ?
There are producers in New Zealand who make Sauvignon I greatly admire such as Seresin, Greywacke, and Dog Point to name a few.
Lithology statistics of the study area computed was 6.34%, 0.94%, 0.93%, 0.93%, 3.27%, 8.24%, 6.57%, 7.46%, 4.44%, 1.22%, 1.12%, 46.20%, 6.12%, 1.05%, and 5.17% for the rock Chunabati formation, composite of Damuda formation and Chunabati formation, composite of Rangit pebble slate and Damuda formation, composite of Rangit pebble slate, Damuda formation and Gorubathan formation, Damuda formation, Darjeeling gneiss, feldspathic greywacke, geabdat sandstone, Gorubathan formation, graphite schist/gneiss, lingtse granite gniess, paro subgroup (paro gneiss), quartzite key beds (paro quartzite), quaternary and recent sediments, and Rangit pebble slate, respectively.
Under plain polarized light of a thin section, the rock has a very "dirty" almost greywacke appearance that at first glance appears to be matrix supported, but it is not a pseudomatrix.
Autumn-colored trees line The Pond (35); snowdrifts blanket Strawberry Fields (106) and Greywacke Arch (20); and aerial shots provide bird's-eye views revealing design layouts of areas such as Conservatory Water, giving a perspective readers could never get by visiting the park.
The spine of the country is made up of the Greywacke Mountains, which start gently in the north and grow ever more precipitous as they turn into the Southern Alps.
The bottom Conglomerate Member consists predominantly of a series of thick beds of conglomerate, sandy conglomerate and greywacke. Coal seams mostly occur in the Lower Coal-bearing Member and the Upper Coal-bearing Member, being in the former present as thick coal seams (max 79.4 m) interlain with coarse sandstones, and in the latter as thin coal seams interlain with fine sandstones [16].
Similarly, developed occurrences of beryl and other gem crystals in stream sediment by chemical and physical alteration of pegmatite, metamorphic and greywacke type units, were described in the state of Minas Gerais, Brazil (Proctor, 1984); the Ratnapura gem deposit, Sri Lanka (Munasinghe and Dissanayake, 1981; Dissanayake et al., 2000); and Ilakaka River gravels in Madagascar (Pezzotta and Simmons, 2001).
In the petrographic analysis of concrete cores, it was found that almost 38% of total aggregates including greywacke, gneiss and quartzite were reactive and responsible for the ASR (Chaudhry and Zaka, 1998).
Balasubramaniam, "Large-scale triaxial testing of greywacke rockfill," Geotechnique, vol.
Suggestions for the starter from Carruthers and Kent are Zuccardi Bonarda, Argentina, [pounds sterling]11.99, or Greywacke Pinot Gris, New Zealand, [pounds sterling]19.99.