Chalk It is formed in the sea by sub-microscopic plankton, which fall to the sea floor and are then consolidated and compressed during diagenesis into chalk rock. Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased. Blackboard chalk manufacture now may utilize mineral chalk, other mineral sources of calcium carbonate, or the mineral gypsum (calcium sulfate). While gypsum-based blackboard chalk is the lowest cost to
Chalk talk use of colors and techniques and the approach talks about the easy use of chalk talk with unnecessary details which can be carried out quickly [makes no sense]. People who are not familiar with this method and would like to give this method a try, this is a perfect book to get access to. A chalk talk was a popular act in vaudeville. A performer used chalk on a blackboard to make changes in a drawing while delivering a monologue. Some performers would do caricatures of audience members. The term also was used to describe an act done with crayons.