Changes

'''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''' is a [[metamorphic rock]] created by the application of intense pressure on mudstones and siltstones.  Because 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 [[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".

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 with 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]].