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A chalk stick is used for writing on a blackboard.
Blackboard chalk is composed of calcium carbonate.
No. Blackboard chalk is calcium sulfate, also known as gypsum. Cliff chalk is calcium carbonate, also known as calcite or limestone.
Chalk
Chalk is made of calcium carbonate, a soft mineral that leaves a visible mark when drawn on a rough surface like a blackboard. When drawn on the blackboard, chalk particles rub off and stick to the surface due to friction, creating a visible line.
A chalkboard is a piece of slate on which to write with chalk and is named after the color "black".
Most of the chalk available in the US is certainly manufactured to be non-toxic and in some cases even hypo-allergenic. The liability is too great for the producer not to insure that it is safe to be around children.
Blackboards are not scratched by chalk because chalk is softer than the material from which the blackboard is constructed. Sand scratches blackboards because it is harder than the material from which a blackboard is made.
Chalk
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Yes, chalk on a blackboard can acquire an electrostatic charge when written or moved on the surface, due to friction between the chalk and the board. This charge can attract or repel other objects nearby.
Chalk is a form of calcium carbonate, so chalk dust is also a form of calcium carbonate.