a sedimentary rock composed of silt or sand particles which have been hardened and cemented.
A variety of sandstone generally characterized by hardness, dark color, and angular grains of quartz, feldspar, and small rock fragments set in matrix of clay-sized particles. Also called lithic sandstone.
A fine-grained conglomerate stone, usually dark grey, quarried on the west side of the Hudson River.
texturally and mineralogically immature sandstones that contain more than 15% clay minerals
A grey to dark grey, poorly-sorted sandstone consisting of angular to subangular grains of quartz and feldspar together with an assortment of small rock fragments set in a compact, fine matrix.
Greywacke (German grauwacke, signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly-sorted, angular grains of quartz, feldspar, and small rock fragments set in a compact, clay-fine matrix. It is a texturally-immature sedimentary rock generally found in Palaeozoic strata. The larger grains can be sand-to-gravel-sized, and matrix materials generally constitute more than 15% of the rock by volume.
