Argillite

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"Argillite" may also refer to Argillite, Kentucky.

A selection of Ancestral Puebloan (Anasazi) turquoise and orange argillite inlay pieces from Chaco Canyon (dated ca. 1020–1140 CE).

An argillite (pronounced /ˈɑrdʒɨlaɪt/) is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillites are basically lithified muds and oozes. They contain variable amounts of silt-sized particles. The argillites grade into shale when the fissile layering typical of shale is developed. Another name for poorly lithified argillites is mudstone. These rocks, although variable in composition, are typically high in aluminium and silica with variable alkali and alkaline earth cations. The term pelitic or pelite is often applied to these sediments and rocks. Metamorphism of argillites produces slate, phyllite, and pelitic schist.

The Haida carvings of Queen Charlotte Islands along the coast of British Columbia are notable aboriginal art treasures created from a type of a hard, fine black silt argillite, sometimes called "black slate", which occurs only at a quarry on a Slatechuck Mountain in the upper basin of Slatechuck Creek, near the town of Skidegate on Graham Island ("chuck" is the Chinook Jargon term for water, and can mean a creek or lake). While at one time, around 1900, it was shipped to Victoria for manufacturing, today the Haida have a monopoly on use of the argillite. This artwork has been of high quality and prized around the world since the Haida first began carving it to sell to sailors around 1800, and modern Haida carvers continue the tradition today, with stunning design and skill.