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 Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased.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. Blackboard acquired Sequoia Retail Systems in May 2016. Though previously a public company, following its 2011 buyout by Providence Equity Partners Blackboard now operates as a private company. The company's headquarters are in Washington, D.C. and it has offices in Asia, Australia, Europe and in several locations in North America. The initial product to be offered by the company was its course management software, first available in 1998. The latest version, Blackboard Learn 9.1, was released in April 2010. This is a learning management system that provides a learning system for course delivery and management for institutions; a community and