:''"Argillite" may also refer to

Argillite, Kentucky Argillite is an unincorporated community on the Little Sandy River in Greenup County, Kentucky, United States. It sits at the southern end of the confluence of Kentucky Routes 1 and 207. The name refers to argillite, a type of stone, related ...

.''

Argillite () is a fine-grained

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

composed predominantly of

indurated Friability ( ), the condition of being friable, describes the tendency of a solid substance to break into smaller pieces under duress or contact, especially by rubbing. The opposite of friable is indurate. Substances that are designated hazardous, ...

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay pa ...

particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts of

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel ...

-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 Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

and

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...

with variable alkali and

alkaline earth The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar properties: they are all ...

cations. The term ''pelitic'' or ''pelite'' is often applied to these

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...

s and rocks.

Metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of ch ...

of argillites produces slate, phyllite, and pelitic

schist Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes ...

Belt Supergroup

The

Belt Supergroup The Belt Supergroup is an assemblage of primarily fine-grained sedimentary rocks and mafic intrusive rocks of late Precambrian (Mesoproterozoic) age. It is more than thick, covers an area of some 200,000 km2 (77,220 sq. mi), and is considered to ...

, an assemblage of rocks of late

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...

( Mesoproterozoic) age, includes thick sequences of argillite, as well as other metamorphosed or semi-metamorphosed mudstones.Schieber, J. 1990. Significance of styles of epicontinental shale sedimentation in the Belt basin, Mid-Proterozoic of Montana, U.S.A. Sedimentary Geology, v. 69, p. 297-312. It is exposed primarily in western

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...

, including the

Bitterroot Valley The Bitterroot Valley is located in southwestern Montana, along the Bitterroot River between the Bitterroot Range and Sapphire Mountains, in the Northwestern United States. Geography The valley extends approximately from Lost Trail Pass in Ida ...

and Bitterroot Mountains, the Missoula area,

Flathead Lake Flathead Lake ( fla, člq̓etkʷ, label= Salish, kut, yawuʔnik̓ ʔa·kuq̓nuk) is a large natural lake in northwest Montana. The lake is a remnant of the ancient, massive glacial dammed lake, Lake Missoula of the era of the last interglacia ...

, and Glacier National Park, and in northern

Idaho Idaho ( ) is a U.S. state, state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Monta ...

. There are also minor occurrences in northeastern

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

and western

Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to t ...

. Excellent outcrops of deep purple, wine red, red, blue, turquoise, and green argillites of the Belt Supergroup can be seen in Glacier National Park in northwestern Montana and in Wolf Creek Canyon along Interstate 15 in west-central Montana.Alt, D.D. and Hyndman, D.W. 1986. Roadside geology of Montana. Mountain Press Publishing Co., Missoula, Montana, 427 p. .

"Black slate"

The Haida carvings of Haida Gwaii along the coast of

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, for ...

are notable aboriginal art treasures created from a type of a hard, fine black silt argillite, sometimes called "black slate". The black slate occurs only at a quarry on a

Slatechuck Mountain Slatechuck Mountain, known as Kaagan in the Haida language, is a summit on south-central Graham Island in Haida Gwaii, formerly known as the Queen Charlotte Islands of the North Coast of British Columbia, Canada. It is located about 9 km wes ...

in the upper basin of

Slatechuck Creek Slatechuck Creek is a short but culturally important stream on Graham Island in the Queen Charlotte Islands of the North Coast of British Columbia, Canada. Only 6.7 km in length , it is located on the south flank of the small range including S ...

, near the town of Skidegate on

Graham Island Graham Island () is the largest island in the Haida Gwaii archipelago (previously known as the Queen Charlotte Islands), lying off the mainland coast of British Columbia, Canada. It is separated by the narrow Skidegate Channel from the other p ...

. At one time, around 1900, it was shipped to Victoria for manufacturing; today the

Haida Haida may refer to: Places * Haida, an old name for Nový Bor * Haida Gwaii, meaning "Islands of the People", formerly called the Queen Charlotte Islands * Haida Islands, a different archipelago near Bella Bella, British Columbia Ships * , a ...

have a monopoly on use of the argillite. Argillite carvings are synonymous with

artwork and are one of the few art forms on the Northwest Coast that is the exclusive right of one cultural group. This artwork has been of high quality and prized around the world since the Haida first began carving it to trade and sell to sailors around 1800. Contemporary Haida carvers continue the tradition.

References

R. V. Dietrich, 2005, ''Gemrocks: Argillite''
Accessed Dec. 22, 2005.

BC Govt MINFILE report
includes history and geological data. * Dauzères, Alexandre, 2004, Ten Years of Argillite Study, Procedia Earth and Planetary Science
USGS argillite
{{Authority control Sedimentary rocks de:Schiefer#Tonschiefer

Belt Supergroup

"Black slate"

See also

References