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
Ant chalk in the United States. Ant chalk Ant chalk, also known as Chinese chalk or 'Miraculous Insecticide Chalk', is an insecticide in the form of normal looking chalk. It contains the pesticides deltamethrin and cypermethrin. While the active ingredients are legal in the United States, the chalk is not legal there. Labeling often falsely claims the chalk is "harmless to human beings and animals" and "safe to use." Chalks have been found to cause serious health problems and deaths. Packaging, often containing lead-based inks, generally does not list ingredients. Despite its illegal status, "Chinese Chalk" is illegally imported from China and