Slate

related topics
{@card@, make, design}
{acid, form, water}
{build, building, house}
{island, water, area}
{specie, animal, plant}
{area, part, region}
{town, population, incorporate}

Slate is a fine-grained, foliated, homogeneous 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. When expertly "cut" by striking with a specialized tool in the quarry, many slates will form smooth flat sheets of stone which have long been used for roofing and floor tiles and other purposes. Slate is frequently grey in color, especially when seen in masse covering roofs. However, slate occurs in a variety of colors even from a single locality; for example, slate from North Wales can be found in many shades of grey, from pale to dark, and may also be purple, green or cyan. Slate is not to be confused with shale, from which it may be formed, or schist. Ninety percent of Europe's natural slate used for roofing originates from Spain.[1]

The word "slate" is also used for some objects made from slate. It may mean a single roofing slate, or a writing slate, traditionally a small piece of slate, often framed in wood, used with chalk as a notepad or noticeboard etc., and especially for recording charges in pubs and inns. The phrase "clean slate" or "blank slate" comes from this use.

Contents

Historical mining terminology

Before the mid-19th century, the terms slate, shale and schist were not sharply distinguished.[2] In the context of underground coal mining, the term slate was commonly used to refer to shale well into the 20th century.[3] For example, roof slate refers to shale above a coal seam, and draw slate refers to roof slate that falls from the mine roof as the coal is removed.[4]

Full article ▸

related documents
Electrum
Laundry
Raku ware
Nu-Wood Decorative Millwork
Fulling
Bowline
Gesso
Apron
Rug making
Fran├žois Tourte
Contact juggling
Berlin wool work
Pilum
Hand saw
Textile arts
Penny
Pole weapon
Marquetry
Pantograph
Figure skating spins
Type design
Ruler
Jigsaw (power tool)
Amethyst
Crayon
Envelope
Pottery
Yellow
Thaler
Slingshot