Slate - Definition and Overview

Alternate meanings in Slate (disambiguation)

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 shingles ('roofing slates' in the UK) because it has two lines of breakability: cleavage and grain. This makes it possible to split slate into thin sheets.

When choosing roofing materials, one must take into consideration the longevity of the roofing material, as well as the installation cost. Slate roofs have been known to last hundreds of years in comparison to the synthetic roof which typically lasts 10-20 years. Synthetic and manufactured roofing materials may initially save money at the time of installation, but the slate roof will last many lifetimes, making it the more permanent, economical choice.

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

See also

List of minerals, tile

External links

• Vermont Roofing Slate (http://www.usedslate.com)
• History of the Welsh slate industry (http://www.slateroof.co.uk)
• Slatesite (http://www.llechicymru.info/index.english.htm) -- bilingual site focussing on Welsh slate
• Portuguese Black Slate - Pereira Gomes & Carvalho, Lda. (http://www.pereiragomes.com)