GRAYWACKE


Meaning of GRAYWACKE in English

n.

or dirty sandstone

Sedimentary rock composed of sand-sized grains in a fine-grained clay matrix.

The sand-sized grains frequently include rock fragments of wide-ranging mineralogies (e.g., pyroxenes, amphiboles, feldspars, and quartz). The clay matrix may constitute up to 50% of the volume. Of the clay minerals, chlorite and biotite are most abundant. The matrix tends to bind the grains strongly and form a relatively hard rock.

Britannica Concise Encyclopedia.      Краткая энциклопедия Британика.