Changes

'''Slate''' is a metamorphic rock created by the application of intense pressure on mudstones and siltstones during periods of [[orogeny]] many millions of years ago.  As the [[mud]] or [[silt]] was laid down in thin layers slate is a highly fissile rock that can be split into thin sheets.

'''Slate''' is a [[metamorphic rock]] created by the application of intense pressure on [[mudstone]]s and siltstones during periods of [[orogeny]] many millions of years ago.  As the [[mud]] or [[silt]] was laid down in thin layers slate is a highly fissile [[rock]] that can be split into thin sheets.

Slate has found use as a roofing or flooring material, for the bed of a [[snooker]] or [[billiards]] table and for writing tablets.  Slates for writing have been in use for many thousands of years and were common well into the twentieth century in many schools. Writing would be accomplished either with a coarse stick of [[chalk]] or a fine stylus made of [[graphite]].  Owing to the ease at which the slate tablets could be cleaned for re-use we get the English [[idiom]] to "start with a clean slate".

Slate has found use as a roofing or flooring material, for the bed of a [[snooker]] or [[billiards]] table and for writing tablets.  Slates for writing have been in use for many thousands of years and were common well into the twentieth century in many [[school]]s. Writing would be accomplished either with a coarse stick of [[chalk]] or a fine stylus made of [[graphite]].  Owing to the ease at which the slate tablets could be cleaned for re-use we get the English [[idiom]] to "start with a clean slate".

When slate undergoes further heat and pressure, it can metamorphose into [[schist]].

When slate undergoes further heat and pressure, it can metamorphose into [[schist]].