Slate (writing) expensive. Slate (writing) A slate is a thin piece of hard flat material, such as the rock also called slate, that is used as a medium for writing. The rock is “a metamorphic rock created by the recrystallization of the minerals in shale from clay to parallel-aligned, flat, flake-like minerals such as mica”. The writing slate consisted of a piece of slate, typically either 4x6 inches or 7x10 inches, encased in a wooden frame. A precise date range for writing slates of this type has not been established. Usually, a piece of cloth or slate sponge was used to clean
Slate types of object made from slate rock. It may mean a single roofing tile made of slate, or a writing slate. These were traditionally a small, smooth piece of the rock, often framed in wood, used with chalk as a notepad or noticeboard, and especially for recording charges in pubs and inns. The phrases "clean slate" and "blank slate" come from this usage. Before the mid-19th century, the terms "slate", "shale" and "schist" were not sharply distinguished. In the context of underground coal mining in the United States, the term slate was commonly used to refer to shale well into