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 Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased.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. United States Court of Appeals for the Federal Circuit. A ruling was made by the Court of Appeals on July 27, 2009 that the 38 patent claims made by Blackboard in its suit against Desire2Learn were invalid. The dispute was resolved, when Blackboard and Desire2Learn announced on December 15, 2009 that each company was settling all ongoing litigation between them and had made a cross-licensing agreement. In April 2010, the firm abandoned patent 6,988,138, and in November that year the company's legal counsel announced the patent's "official termination" and stated that Blackboard had ended its appeals. Blackboard Inc. Blackboard Inc.