slate

1. A fine-grained metamorphic rock that splits into thin, smooth-surfaced layers.
2. 1. A piece of this rock cut for use as roofing or surfacing material or as a writing surface.
   2. A writing tablet made of a similar material.
3. A record of past performance or activity: start over with a clean slate.
4. A list of the candidates of a political party running for various offices.
5. A dark or bluish gray to dark bluish or dark purplish gray.

1. Made of a fine-grained metamorphic rock: a slate roof.
2. Of the color slate.

1. To cover (a roof, for example) with slate.
2. To put on a list of candidates.
3. To schedule or designate: Our professor has slated the art history lecture for Thursday afternoon; was slated to direct the studio's next film.

[Middle English sclate, from Old French esclate, splinter, feminine of esclat. See slat.]

For more information on slate, visit Britannica.com.

Any of the deformed fine-grained, mica-rich rocks that are derived primarily from mudstones and shales, containing a well-developed, penetrative foliation that is called slaty cleavage. Slaty cleavage is a secondary fabric element that forms under low-temperature conditions (less than 540°F or 300°C), and imparts to the rock a tendency to split along planes. It is a type of penetrative fabric; that is, the rock can be split into smaller and smaller pieces, down to the size of the individual grains. If there is an obvious spacing between fabric elements (practically, greater than 1 mm), the fabric is called spaced. Slates typically contain clay minerals (for example, smectite), muscovite/illite, chlorite, quartz, and a variety of accessory phases (such as epidote or iron oxides). Under increasing temperature conditions, slate grades into phyllite and schist. See also Argillaceous rocks; Clay minerals; Phyllite; Schist; Shale.

Slaty cleavage is defined by a strong dimensional preferred orientation of clay in a very clay rich, low-grade metamorphic rock, and the resulting rock is a slate. Slaty cleavage tends to be smooth and planar. Coupled with the penetrative nature of slaty cleavage, these characteristics enable slates to split into very thin sheets. This and the durability of the rock are reasons why slates are used in the roofing industry, in the tile industry, and in the construction of pool tables.

noun

A list of candidates proposed or endorsed by a political party: lineup, ticket. See politics.

verb

To enter on a schedule: program, schedule. See remember/forget.

Idioms beginning with slate:
slated for, be

In addition to the idiom beginning with slate, also see clean slate.

A weak sedimentary rock, easily split along thin layers of bedding, formed by the compression of shales by the overlying rocks.

A hard, brittle metamorphic rock consisting mainly of clay minerals, characterized by good cleavage along parallel planes; used extensively as dimension stone in thin sheets for flooring, roofing, panels (both decorative and electrical), and chalkboard, and in granular form as surfacing on composition roofing.

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Slate
—  Metamorphic Rock  —
Slate
Composition
Primary	quartz, muscovite/illite
Secondary	biotite, chlorite, hematite, pyrite

Slate Macro (~ 6 cm long and ~ 4 cm high)

For other uses, see Slate (disambiguation).

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. The result is a foliated rock in which the foliation may not correspond to the original sedimentary layering. Slate is frequently grey in colour especially when seen en masse covering roofs. However, slate occurs in a variety of colours even from a single locality. For example slate from North Wales can be found in many shades of grey from pale to dark and may also be purple, green or cyan.

Slate is not to be confused with shale, from which it may be formed, or schist.

Contents 1 Historical mining terminology 2 Chemical composition 3 Uses 3.1 Slate in buildings 3.2 Other uses 4 Slate extraction 4.1 In Eurasia 4.2 In the Americas 5 Fossils 6 References 7 External links 8 See also

Historical mining terminology

Before the mid 19^th century, the terms slate, shale and schist were not sharply distinguished.^[1] In the context of underground coal mining, the term slate was commonly used to refer to shale well into the 20^th century.^[2] For example, roof slate refers to shale above a coal seam, and draw slate refers to roof slate that falls from the mine roof as the coal is removed.^[3]

Chemical composition

Slate is mainly composed of quartz and muscovite or illite, often along with biotite, chlorite, hematite, and pyrite and, less frequently, apatite, graphite, kaolin, magnetite, tourmaline, or zircon as well as feldspar. Occasionally, as in the purple slates of North Wales, ferrous reduction spheres form around iron nuclei, leaving a light green spotted texture. These spheres are sometimes deformed by a subsequent applied stress field to ovoids, which appear as ellipses when viewed on a cleavage plane of the specimen.

Uses

Slate roof

Slate in buildings

Slate can be made into roofing slates, also called roofing shingles, installed by a slater.^[4] Slate has two lines of breakability: cleavage and grain, which make it possible to split the stone into thin sheets. When broken, slate retains a natural appearance while remaining relatively flat and easily stackable.

Slate tiles are often used for interior and exterior flooring, stairs, walkways, and wall cladding. Tiles are installed and set on mortar and grouted along the edges. Chemical sealants are often used on tiles to improve durability and appearance, increase stain resistance, reduce efflorescence, and increase or reduce surface smoothness. Tiles are often sold gauged, meaning that the back surface is ground for ease of installation. Slate flooring can however be slippery when used in external locations subject to rain. Slate tiles were used in 19th century UK building construction (apart from roofs) and in slate quarrying areas such as Bethesda, Wales there are still many buildings wholly constructed of slate. Slates can also be set into walls to provide a rudimentary damp-proof membrane. Small offcuts are used as shims to level floor joists. In areas where slate is plentiful it is also used in pieces of various sizes for building walls and hedges, sometimes combined with other kinds of stone.

Other uses

John Betjeman's grave in Cornwall with inscription on slate

Because it is a good electrical insulator and fireproof, it was used to construct early 20th century electric switchboards and relay controls for large electric motors. Fine slate can also be used as a whetstone to hone knives.

Due to its thermal stability and chemical inertness, slate has been used for laboratory bench tops and for billiard table tops. In 18th and 19th century schools, slate was extensively used for blackboards and individual writing slates for which slate or chalk pencils were used. They were largely used in the 20th century, though writing slates were largely replaced by lined paper and notebooks, and slates still continue in wide usage.

In areas where it is available, high-quality slate is used for gravestones and commemorative tablets, and by artists in various genres.

Slate is often used as a decor in freshwater aquariums. Slate will not alter the chemistry of water (except in the slate containing feldspar which may leach silicates into the water resulting in excess diatom growth in marine aquaria).

Slate is used in some desert reptile enclosures because it holds heat very well. Traditional Japanese Go equipment uses slate for the black pieces.

Slate extraction

Exhibition Slate mine Fell

Historical Pit Vogelsberg 1 at Fell

See main article at Slate industry

In Eurasia

Slate-producing regions in Europe include Wales (see slate industry in Wales), Cornwall (famously the village of Delabole), and Cumbria (see Burlington Slate Quarries, Honister Slate Mine and Skiddaw Slate) in the United Kingdom; parts of France (Anjou, Ardennes, Bretagne, Savoie); Belgium (Ardenne); Liguria in northern Italy especially between the town of Lavagna (which means chalkboard in Italian) and Fontanabuona valley; Portugal especially around Valongo in the north of the country; Germany's (Moselle River-region, Hunsrück, Eifel, Westerwald, Thuringia and north-Bavaria); Alta, Norway (actually schist not a true slate) and Galicia. Some of the slate from Wales and Cumbria is colored slate (non-blue): (purple and formerly green in Wales) and (green in Cumbria). China has vast slate deposits; in recent years its export of finished and unfinished slate has increased: it has slate in various colors.

In the Americas

Slate is abundant in Brazil (the second biggest producer of slate) around Papagaio in Minas Gerais (responsible for 95% of the extraction of slate in Brazil), the east coast of Newfoundland, the Slate Belt of Eastern Pennsylvania, and the Slate Valley of Vermont and New York, where colored slate is mined in the Granville, New York area.

A major slating operation existed in Monson, Maine during the late 19th and early 20th centuries. The slate found in Monson is usually a dark purple to blackish color, and many local structures are still roofed with slate tiles. The roof of St. Patrick's Cathedral was made of roofing slate from Monson, as was the headstone of John F. Kennedy.^{[citation needed]}

Slate is also found in the Arctic and was used by the Inuit to make the blades for ulus.

Fossils

Shale can metamorphise into slate; sometimes the fossils may remain intact.

Because slate was formed in low heat and pressure, compared to a number of other metamorphic rocks, some fossils can be found in slate; sometimes even microscopic remains of delicate organisms.^[5]

References

1. ^ R. W. Raymond, Slate, A Glossary of Mining and Metallurigical Terms, American Institute of Mining Engineers, 1881; page 78.
2. ^ Albert H. Fay, Slate, A Glossary of the Mining and Mineral Industry, United States Bureau of Mines, 1920; page 622.
3. ^ J. Marvin Weller, ed.,Supplement to the Glossary of Geology and Related Sciences, American Geological Institute, 1960; page 18.
4. ^ Hart, Diane (1991) The building slates of the British Isles. Watford: Building Research Establishment ISBN 0851254837
5. ^ BBC Video : David Attenborough : Lost Worlds, Vanished Lives

• Page, William (ed.) (1906) The Victoria History of the County of Cornwall; vol. I. (Chapter on quarries.) Westminster: Constable

External links

• AditNow - Photographic database of mines
• History of the Welsh slate industry
• John T F Turner - A Familiar Description of the Old Delabole Slate Quarries, 1864
• Granville Slate Museum
• Hower’s Lightning Slate Reckoner (1884/1904), by F. M. Hower, Cherryville, Penn., on Stone Quarries and Beyond (PDF/18.95 MB)

See also

• List of rock types
• Tile
• National Slate Museum
• Fell Exhibition Slate Mine
• Slate industry in Wales
• Slate and stylus

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - skifer, skifertagsten, tavle, hinkesten
v. tr. - lægge skifertag på, sætte på liste, foreslå, beramme, forudbestemme
adj. - skifergrå, skifer-

idioms:

• slate PC    PC hvor man kan skrive data ind med en lyspen
• wipe the slate clean    begynde på en frisk

Nederlands (Dutch)
lei, leisteen, grijs, kandidatenlijst, kandideren, afkraken

Français (French)
n. - ardoise, (US) liste de candidature
v. tr. - couvrir (qch) d'ardoises, (GB) taper sur, blâmer, (US, Pol) mettre (qn) sur la liste, (US) avoir de fortes chances de
adj. - d'ardoise

idioms:

• slate PC    (Comput) ordinateur bloc-notes
• wipe the slate clean    faire table rase (du passé)

Deutsch (German)
n. - Schiefer, Schiefertafel, Schieferplatte, Kandidatenliste
v. - vorsehen, scharf kritisieren
adj. - schiefergrau

idioms:

• slate PC    Mobil-PC mit einer Oberfläche für Dateneingabe mit einem elektr. Kuli
• wipe the slate clean    einen Schlußstrich ziehen

Ελληνική (Greek)
n. - (μαθητική) πλάκα, αβάκιο, (γεωλ.) σχιστόλιθος, (ΗΠΑ) λίστα υποψηφίων για αξίωμα
v. - καλύπτω (στέγη κ.λπ.) με πλάκες σχιστόλιθου, (ΗΠΑ) προετοιμάζω εκδήλωση, (ΗΠΑ) προτείνω κάποιον ως υποψήφιο, (Βρετ., καθομ.) επικρίνω, κατσαδιάζω
adj. - από πλάκες σχιστόλιθου

idioms:

• slate PC    φορητός υπολογιστής με ηλεκτρονική γραφίδα
• wipe the slate clean    γυρίζω νέα σελίδα

Italiano (Italian)
stroncare, ardesia, lavagna, lista dei candidati

idioms:

• a clean slate    tabula rasa
• wipe the slate clean    fare tabula rasa, ricominciare daccapo

Português (Portuguese)
n. - ardósia (f), cinzento azulado (m), lousa (f)
v. - assentar, censurar, criticar
adj. - critico (m)

idioms:

• a clean slate    começar de novo
• wipe the slate clean    esquecer o passado e começar vida nova

Русский (Russian)
шиферная плитка, грифельная доска, шиферный сланец, список, программа (состязаний), аспидный цвет, разгромная рецензия, крыть шифером, заносить в список кандидатов, выдвигать для рассмотрения, назначать (на какое-то время), дать нагоняй, выпороть

idioms:

• a clean slate    безупречная репутация, полный порядок (в делах)
• wipe the slate clean    забыть старые ошибки и начать с чистого листа

Español (Spanish)
n. - pizarra, lista de candidatos
v. tr. - echar una bronca, vapulear, castigar
adj. - de pizarra, pizarreño, apizarrado

idioms:

• slate PC    (comp) notebook con superficie para ingresar datos con un lápiz electrónico
• wipe the slate clean    hacer borrón y cuenta nueva

Svenska (Swedish)
n. - skiffer, takplatta, takskiffer, griffeltavla, skiffergrått, preliminär kandidatlista för ett val
v. - täcka med skiffer, skiffertäcka, göra ner, läxa upp, tufsa till, föreslå som kandidat, tillkännage, planera in, avtala, utsätta, förutbestämma
adj. - skiffergrå

中文（简体）(Chinese (Simplified))
板岩, 石片, 石板, 铺石板, 痛打, 责骂, 暗蓝灰色的, 含板岩的

idioms:

• slate PC    板形计算机
• wipe the slate clean    把以往的过错或不和债务等一笔勾销

中文（繁體）(Chinese (Traditional))
n. - 板岩, 石片, 石板
v. tr. - 鋪石板, 痛打, 責罵
adj. - 暗藍灰色的, 含板岩的

idioms:

• slate PC    板形電腦
• wipe the slate clean    把以往的過錯或不和債務等一筆勾銷

한국어 (Korean)
n. - 슬레이트, 짙은 청회색, (지명) 후보자 명부
v. tr. - (지붕을) 슬레이트로 이다, 후보자 명단에 올리다, 예정하다
adj. - 석판질의, 석판색

日本語 (Japanese)
n. - スレート, 粘板岩, スレート色, 候補者名簿, 石板
v. - スレートでふく, 候補者名簿に載せる, 予定する, 予定させる, 酷評する

العربيه (Arabic)
‏(الاسم) صخر يسهل قطعه ألى ألواح تكسى بها ألسقوف, لوح أردوازي للكتابه, سجل أعمال أو أحداث (فعل) يسجل ألاسماء, يكسو بألواح أردوازيه (صفه) مكسو بألواح أردوازيه‏

עברית (Hebrew)
n. - ‮צפחה, רעף, לוח צפחה, רשימת מועמדים‬
v. tr. - ‮כיסה ברעפים, הציע מועמדות, הועיד, תכנן, גינה, תקף, קטל‬
adj. - ‮אפור-כחול, עשוי רעפים‬

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