slate


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slate,

fine-grained rockrock,
aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic.
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 formed when sedimentary rocks such as shaleshale,
sedimentary rock formed by the consolidation of mud or clay, having the property of splitting into thin layers parallel to its bedding planes. Shale tends to be fissile, i.e., it tends to split along planar surfaces between the layers of stratified rock.
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 are metamorphosed by great pressure. Slate splits into perfectly cleaved, broad thin layers; this characteristically regular and planar cleavage is called slaty cleavage. In the formation of slate, pressure causes the flaky minerals within the sedimentary rock, such as mica, clay, and chlorite, to be reoriented; the flat faces of the minerals lie at right angles to the source of the pressure, and the planes of easy cleavage are also at right angles to the source of the pressure. The rock is not necessarily compressed in the same direction as the sedimentary layers were originally laid down, and because the compression crumples and deforms the original sedimentary layers, the planes of slaty cleavage usually cut through the old bedding planes. Slate is intermediate in hardness between mica schistsschist
, metamorphic rock having a foliated, or plated, structure called schistosity in which the component flaky minerals are visible to the naked eye. Schists are distinguished from the other foliated rocks, slates and gneisses, by the size of their mineral crystals; these are
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 and shale; the better grades are used for roofing. Its characteristic color is gray-blue. Slate is mined in Maine, Vermont, Pennsylvania, Georgia, Lake Superior, and the Rocky Mts.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/

slate

A hard, brittle metamorphic rock characterized by good cleavage along parallel planes; used as cut stone in thin sheets for flooring, roofing, and panels, and in granular form as surfacing on composition roofing.
See also: Stone
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Slate

 

a schistous, sedimentary rock used for roofing. It consists of argillaceous minerals (for the most part, various hydromicas and chlorite) whose particles are usually arranged in strictly parallel lines. This structure gives slate a sharply defined schistosity, that is, the capacity for cleavage into thin lamina. Slate does not fall apart in water and has the characteristics of geosynclinal sediments. It is formed by the compaction of clays and their partial recrystallization under pressure at considerable depths as well as by the effect of dynamic metamorphism. When it undergoes further change, it becomes a phyllte or a chlorite slate.

The largest known deposits of slate in the USSR are located in the Caucasus and the Urals. Slate is used as roofing material; in the production of low-voltage switchboards, knife switches, and other apparatus in the electrical industry; and in the production of certain structural components (panels for the interior facing of rooms). Slate is also used in a crushed, roasted, and aerated form as filler for certain types of concrete, large wall blocks, and for cladding ruberoid(roof-sheeting material).

V. P. PETROV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

slate

[slāt]
(petrology)
A group name for various very-fine-grained rocks derived from mudstone, siltstone, and other clayey sediment as a result of low-degree regional metamorphism; characterized by perfect fissility or slaty cleavage which is a regular or perfect planar schistosity.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

slate

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.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

slate

1. 
a. a compact fine-grained metamorphic rock formed by the effects of heat and pressure on shale. It can be split into thin layers along natural cleavage planes and is used as a roofing and paving material
b. (as modifier): a slate tile
2. a dark grey colour, often with a purplish or bluish tinge
3. Chiefly US and Canadian a list of candidates in an election
4. Films
a. the reference information written on a clapperboard
b. Informal the clapperboard itself
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

slate

Another name for a tablet. In 2010, HP introduced tablets under the Slate brand. See Tablet PC and tablet.
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References in periodicals archive ?
Philip Brooke, managing director of EBP Building Products in Blackburn, Lancs, sources slate from Brazil and China.
"For Google's first-party hardware efforts, we'll be focusing on Chrome OS laptops and will continue to support Pixel Slate."
She said: "Following recent discussions with the local community in Blaenau Ffestiniog I welcome the decision taken by Llechwedd to use 'Llechwedd' as its official name again following concerns about 'Slate Mountain'.
Since December 2016, Slate has completed a total of 11 portfolio acquisitions in Germany.
The challenger slate, Lindenhurst United for Change, includes Milburn Elementary District 24 board member Casandra Slade, her former Milburn colleague Trak Patel and Stacey Kramer, the founder of the Lake County chapter of the Brady Campaign to Prevent Gun Violence.
For that reason, Third Point filed the new shorter slate of independents with the Securities and Exchange Commission, it said in a statement.
Parang ngayon 'yung mas matimbang ngayon na hindi punuin 'yung slate, parang strategy (The debate in the coalition is whether to field 12 candidates or less.
Villagers said they were disappointed to discover that Spanish slate was to be used on the houses.
Testing then took place with the Vermont Slate on the same 3/8" wood deck, firing the 4" hail at 183mph, well beyond the typical terminal velocity of falling hail that size (approximately 100mph).
But fans of the Bard have been outraged at the discovery that cutprice Spanish slate is being used to refurbish the West Dunbartonshire Council-owned landmark.
Anwyl Construction used the distinctive dark blue and grey slate from the Cwt y Bugail Quarry and Welsh slate walling from a local supplier to ensure a strong local connection with the area.