Chalk It is formed in the sea by sub-microscopic plankton, which fall to the sea floor and are then consolidated and compressed during diagenesis into chalk rock. Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased. Blackboard chalk manufacture now may utilize mineral chalk, other mineral sources of calcium carbonate, or the mineral gypsum (calcium sulfate). While gypsum-based blackboard chalk is the lowest cost to
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