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 October 2017, Blackboard partnered with OpenEd to integrate OER with Learning Management Systems. Blackboard Learn provides users with a platform for communication and sharing content. Blackboard Inc has had several legal issues, including faulty patent rights claims. In addition, a number of educational institutions, teachers, and students have expressed concerns about the reliability of Blackboard. McMaster University in Hamilton, Ontario, Canada, has replaced their Blackboard system after multiple problems during one year of use. Citing numerous glitches and high costs, many universities are turning to the cheaper, open source alternative Moodle, including Montana State University, Vassar College, California State University,