Chalk produce, and thus widely used in the developing world, calcium-based chalk can be made where the crumbling particles are larger and thus produce less dust, and is marketed as "dustless chalk". Colored chalks, pastel chalks, and sidewalk chalk (shaped into larger sticks and often colored), used to draw on sidewalks, streets, and driveways, are primarily made of gypsum. Chalk is a source of quicklime by thermal decomposition, or slaked lime following quenching of quicklime with water. In southeast England, deneholes are a notable example of ancient chalk pits. Such bell pits may also mark the sites of ancient flint mines,
Chalk talk Chalk talk A chalk talk is a monologue presentation done while the speaker draws. It is usually done with chalk, hard crayon, or pastel, or with dry-erase markers on a whiteboard. The chalk talk method of teaching focuses on the blackboard and the lecturer's voice and also the activities – to be precise, the physical activities. This method can be preferred for presenting lectures and talks. Because of an article in the "Deseret News" published on September 17, 1895 the roots of "chalk talks" can be traced to the Methodist church - and a singular individual - Mr. Frank Beard