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 Learn LLC and were developing a software product that would power online education and be scalable for wider institutional application. At the same time, Matthew Pittinsky and Michael Chasen formed Blackboard LLC and were contracted to help lead the formation of the Educause IMS standards group for online education technology. The two groups merged to form Blackboard Inc., which then developed the Blackboard Learning System. In 2015 the company announced a major upgrade to the user experience, called Ultra. According to company statements, Ultra is to be an optional user interface sitting on top of the existing Learn 9.1 architecture. In