Who invented chalk?

The first real blackboard was invented by Zhan Mu Deuce Piran, an educator from Essence University. He is the headmaster of Laozhi Edinburgh Middle School, and teaches geography with a blackboard and colored chalk invented by himself. It has the function of repeated erasure. ? 180 1 year, George Barron, a math teacher at West Point Military Academy, became the first American to teach with a big blackboard. But it was not until more than twenty years later that Samuel Hall, an American educator, registered the first blackboard patent. He painted a pine board black. At the same time, some people draw lime, plaster of Paris and pot smoke directly on the wall of the classroom. 1990' s water mill glass, now color coated steel plate, composite plate, etc. Used as blackboard material. ? At present, the types of blackboards are divided into blackboard, green board and whiteboard in color, flat board and arc board in surface shape, bracket movable board, push-pull board, lifting board and magnetic blackboard in structure, and teaching blackboard, office whiteboard, billboard and display board in use ... Teaching blackboard also includes electronic blackboard, multifunctional combination board, interactive electronic whiteboard and projection board with screen.