Blackboard Chalk Isn’t Really Chalk at All
Ubiquitous in many classroom since the 19th century , glass and chalkboards are familiar to most of us . white-hot , powdery and prone to sticking to those surfaces where it is put ( and just as soft to pass over aside ) , chalk and its come with control board are excellent instructional assistance . Notably , however , most chalk today is n’t technically chalk at all , but gypsum ....