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
Rock Chalk, Jayhawk preceded by the Kansas alma mater "Crimson and the Blue,” and followed by the fight song, "I'm a Jayhawk.” Since the early 1990's, Kansas fans have been known to do the slow repetition of "Rock chalk... Jay-Hawk... KU" when the Jayhawks are believed to be safely ahead, and victory is guaranteed. Rock Chalk, Jayhawk "Rock Chalk, Jayhawk" (a.k.a. the "Rock Chalk" chant) is a chant used at University of Kansas Jayhawks sporting events. The chant is made up of the phrase "Rock chalk, Jayhawk, KU". The chant was first adopted by the university's science club in 1886. Chemistry professor E.H.S.