Slate

Slate is a fine-grained, homogeneous, sedimentary rock composed of clay or volcanic ash which has been metamorphosed (foliated) in layers (bedded deposits). 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.

Related Topics:
Sedimentary rock - Clay - Volcanic - Ash - Metamorphosed - Roof - Shingle - United States

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Fine slate can also be used to hone knives.

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Slate is mainly composed of quartz and muscovite (a mica), often along with biotite, chlorite, and hematite, or, less frequently, apatite, graphite, kaolin, magnetite, tourmaline, or zircon.

Related Topics:
Quartz - Muscovite - Mica - Biotite - Chlorite - Hematite - Apatite - Graphite - Kaolin - Magnetite - Tourmaline - Zircon

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Some of the finest slates in the world come from Portugal, Wales in the United Kingdom, the east coast of Newfoundland, and the "Slate Valley" of Vermont and New York.

Related Topics:
Portugal - Wales - United Kingdom - Newfoundland - Vermont - New York

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