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. On July 1, 2011, Blackboard agreed to a $1.64 billion buyout by an investor group led by Providence Equity Partners, completed on October 4, 2011. Following the sale, Providence Equity Partners merged Edline, its K-12 learning system, with Blackboard. Edline was later renamed Blackboard Engage. According to a TechCrunch article from 2012, despite its success, Blackboard had become "one of the most disliked — even detested — companies in education." In December 2011, "Fast Company" reported that 93% of respondents to the Amplicate customer opinion survey "hate" the company. In September 2017, Blackboard announced its expansion to the Indian Educational