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Slate
*** Shopping-Tip: Slate
{{otheruses}}
Image:SlateUSGOV.jpg thumb|Slate
'''Slate''' is a fine-grained, homogeneous,
metamorphic rock which was derived from an original
sedimentary rock composed of
clay or
volcano volcanic ash (volcanic) ash through low grade regional
metamorphism. The result is a
Foliation (geology) foliated rock in which the foliation may not correspond to the original sedimentary layering.
Slate is mainly composed of
quartz and
muscovite or
illite, often along with
biotite,
chlorite,
hematite, and
pyrite along with, less frequently,
apatite,
graphite,
kaolin,
magnetite,
tourmaline, or
zircon.
Slate can be made into
roofing slates (sometimes called ''roofing
shingles'' in the
United States), because it has two lines of breakability: cleavage and grain. This makes it possible to split slate into thin sheets. Fine slate can also be used as a
whetstone (tool) whetstone to hone knives. Because of 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 ''
Chalkboard blackboards'' and individual ''writing slates'' for which slate pencils were used.
Slate producing regious include
Cornwall (famously the town of
Delabole) and
Wales in the
United Kingdom,
Portugal, the east coast of
Newfoundland, and the ''Slate Valley'' of
Vermont and
New York.
Slate is also found in the
Arctic and was used by the
Inuit to make the blades for
ulus.
See also
*
List of rocks
*
Tile
External links
-
History of the Welsh slate industry
-
Slatesite — bilingual site focusing on Welsh slate
-
John T F Turner - A Familiar Description of the Old Delabole Slate Quarries, 1865
Category:Metamorphic rocks
Category:Materials
Category:Stone
cy:Llechfaen
de:Schiefer
et:Kilt
eo:Ardezo
fr:Ardoise
nl:Leisteen
pt:Ardósia
sv:Skiffer
*** Shopping-Tip: Slate
