Blackboard ‘chalk’ are produced especially for use with blackboards in white and also in various colours. White chalk sticks are made mainly from calcium carbonate derived from mineral chalk rock or limestone, while colored or pastel chalks are made from calcium sulfate in its dihydrate form, CaSO·2HO, derived from gypsum. Chalk sticks containing calcium carbonate typically contain 40–60% of CaCO (calcite). As compared to whiteboards, blackboards still have a variety of advantages: On the other hand, chalk produces dust, the amount depending on the quality of chalk used. Some people find this uncomfortable or may be allergic to it, and according
Blackboard Jungle Blackboard Jungle Blackboard Jungle is a 1955 social commentary film about teachers in an interracial inner-city school, based on the novel "The Blackboard Jungle" by Evan Hunter and adapted for the screen and directed by Richard Brooks. It is remembered for its innovative use of rock and roll in its soundtrack and for the unusual breakout role of a black cast member, future Oscar winner and star Sidney Poitier as a rebellious, yet musically talented student. In 2016, the film was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically,