Blackboard

A blackboard or a chalkboard is a reusable writing surface on which text or drawings are made with sticks of calcium sulphate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone.

For other uses, see Blackboard (disambiguation).
"Chalkboard" redirects here. For other uses, see Chalkboard (disambiguation).

Blackboard
NASA scientist Homer E. Newell Jr. explaining principles of altitude, pressure, and temperature, c. 1973
Other namesChalkboard, writing-board
UsesReusable writing surface on which text or drawings are made
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