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
What Are Little Boys Made Of? a episode titled What Are Little Girls Made Of? was released, describing the culmination of Nurse Chapel's search for her fiancée (Korby), and the discovery of his plans for conquest. The nursery rhyme's notion of the composition of girls was the inspiration behind the Cartoon Network original series "The Powerpuff Girls", in which Professor Utonium creates the Powerpuff Girls by adding together sugar, spice, and everything nice (and Chemical X by mistake). In the same show, Mojo Jojo gathers the snips and snails and a puppy-dog tail and flushes them down a toilet to create the Rowdyruff Boys. It also