Clay Slate Wacke

Clay

Clay is a type of fine-grained natural soil material containing clay minerals. Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as a reddish or brownish colour from small amounts of iron oxide.

Slate

Slate is a fine-grained, foliated, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade, regional metamorphism. It is the finest-grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.

Greywacke

Greywacke or graywacke is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or sand-size lithic fragments set in a compact, clay-fine matrix. It is a texturally immature sedimentary rock generally found in Paleozoic strata. The larger grains can be sand- to gravel-sized, and matrix materials generally constitute more than 15 percent of the rock by volume.

Slate gray

Slate gray is a moderate shade of gray with a slight azure tinge, which represents the average color of slate, a metamorphic rock often used in stonemasonry. As a tertiary color, slate is an equal mix of purple and green pigments.

clay

Noun

1. A mineral substance made up of small crystals of silica and alumina, that is ductile when moist; the material of pre-fired ceramics.
2. An earth material with ductile qualities.

Verb

1. To add clay to or to spread clay onto.
2. To purify using clay.

slate

Noun

1. A flake or piece of certain types of stone that tend to cleave into thin layers.

Adjective

1. Having the bluish-grey colour of slate (noun etymology 1, noun sense 4).

wacke

Noun

1. A soft, earthy, dark-coloured rock or clay derived from the alteration of basalt.