Chalk produce, and thus widely used in the developing world, calcium-based chalk can be made where the crumbling particles are larger and thus produce less dust, and is marketed as "dustless chalk". Colored chalks, pastel chalks, and sidewalk chalk (shaped into larger sticks and often colored), used to draw on sidewalks, streets, and driveways, are primarily made of gypsum. Chalk is a source of quicklime by thermal decomposition, or slaked lime following quenching of quicklime with water. In southeast England, deneholes are a notable example of ancient chalk pits. Such bell pits may also mark the sites of ancient flint mines,
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