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 Most people first encounter the word "chalk" in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased.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. initial public offering raised an estimated $70 million for the company, making it the second-most successful technology IPO of that year. In 2006, Blackboard completed the acquisition of its largest competitor, WebCT Inc, enlarging its share of the higher education market to between 65 and 75 percent. Over the next five years, the company invested in a series of new products and acquisitions, including Blackboard Xythos, Blackboard Connect, Blackboard Mobile, Blackboard Collaborate, and Blackboard Analytics., thus expanding beyond the learning management system market. By 2011, the firm's products were used by over half of colleges and universities in the US.