Blackboard ‘chalk’ are produced especially for use with blackboards in white and also in various colours. White chalk sticks are made mainly from calcium carbonate derived from mineral chalk rock or limestone, while colored or pastel chalks are made from calcium sulfate in its dihydrate form, CaSO·2HO, derived from gypsum. Chalk sticks containing calcium carbonate typically contain 40–60% of CaCO (calcite). As compared to whiteboards, blackboards still have a variety of advantages: On the other hand, chalk produces dust, the amount depending on the quality of chalk used. Some people find this uncomfortable or may be allergic to it, and according
Blackboard Inc. the CourseInfo brand was dropped in 2000. As an extension of CourseInfo's original two weeks for free courses, the company provided a hosted version "CourseSites" for teachers to try out for free. After having raised its seed round, the new company made a profit in its first year, and its sales in 1998 approached US$1 million. Other early products included Blackboard Classroom and Blackboard Campus both derivatives of the original platform. In 2000, Blackboard acquired iCollege/College Enterprises Inc.'s campus card, introducing commerce capability to Blackboard's portfolio. By 2006, the firm's learning platform software was used in more than 40% of