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. developer, increased Blackboard's client base to nearly 6,000 educational institutions, companies and government agencies. The company has also made acquisitions in order to expand its product base with other education-related services and software. Such acquisitions include: NTI Group in 2008, which became the basis for Blackboard Connect; providers of online and mobile collaboration tools, Wimba, Inc. and Elluminate, Inc. in 2010, to form Blackboard Collaborate; iStrategy in December 2010, which led to the creation of Blackboard Analytics; Presidium Inc. in 2011, which developed into Blackboard Student Services. Following the company's merger with Edline in 2011, Edline was later renamed Blackboard