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 Inc. Blackboard Inc. Blackboard Inc. is an educational technology company with corporate headquarters in Washington, D.C.. It is known for Blackboard Learn, a learning management system. The company's CEO is William L. Ballhaus, formerly president and CEO of SRA International, who was also named chairman and president on January 4, 2016, following the resignation of Jay Bhatt, who had led Blackboard since October 2012. The firm provides education, mobile, communication, and commerce software and related services to clients including education providers, corporations and government organizations. The software consists of seven platforms called Learn, Transact, Engage, Connect, Mobile, Collaborate and Analytics that