This rock is formed from pelitic sediments— clays, mudstones, shales, and fine-grained tuff. It contains clay minerals, quartz, mica, and feldspar. Organic matter, such as graphite, give black slate its dark color.

TEXTURE This is a fine-grained rock. It has the characteristic perfect, slaty cleavage produced by the alignment of flaky minerals, such as mica, making it easily split into thin sheets.

ORIGIN Forms when fine-grained, pelitic sediments, such as mudstones or shales, undergo regional metamorphism at low temperatures and low pressures.

Group: METAMORPHIC

Grain size: Fine

Classification: Regional

Pressure: Low

Temperature: Low

Structure: Foliated

Useful slate

Slate is a popular building material and has many uses. Pieces of slate were used as the original chalkboards and it is a common material today for floors because is lasts a long time.