See the Related Link. It has some information about the history of chalkboards used in schools.
Measure the dimensions of the chalkboard, then cut material to those dimensions.
Chalk.
near a chalk board
Chalk
Chalk
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The Luhya translation of the English words 'chalk board' is "lisisi lie ichoka".
Chalk is used on the black board because chalk is easy to write with on a black board.
Nature's chalk is limestone--hard. Blackboard chalk is soft--gypsum.
5x2x1.5
It would be an insulator- chalk board erasers normally consist of two parts, a wooden handle and a soft pad that wipes off the chalk from the board. Neither of these parts are conductors of electricity.
Chalk is Calcium Carbonate, aka CaCO3, so it's only one substance.