Slate
Slate is a fine-grained, ,
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.
Encyclopedia
Slate is a fine-grained, ,
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.
Chemical composition
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.
Uses of slate
Slate can be made into
roofing slates, also called
roofing shingles, 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 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
blackboards and individual
writing slates for which slate pencils were used.
Slate tiles are often used for interior and exterior flooring or 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 efflorence, and increase or reduce surface smoothness. Tiles are often sold gauged, meaning that the back surface is ground for ease of installation.
Slate is often used as a decor in freshwater aquariums. Slate will not alter the chemistry of water. When broken, slate produces a natural appearance while remaining relatively flat and can be easily stacked. Silicon glue adheres to slate, creating a non-toxic bond to secure it.
Traditional Go equipment uses slate for the black pieces.
Slate extraction
Slate-producing regions include
Cornwall and
Wales in the
United Kingdom ,
Portugal, the east coast of
Newfoundland, the Slate Belt of Eastern
Pennsylvania, and the Slate Valley of
Vermont and
New York. Granville, New York, of the Slate Valley claims to be the colored slate capital of the world.
Slate is also found in the
Arctic and was used by the
Inuit to make the blades for
ulus. China has vast slate deposits, in recent years the export of finished and unfinished slate from China has increased.
See also
...
External links
- — bilingual site focusing on Welsh slate
