Calcium sulfate an unusual property: when mixed with water at normal (ambient) temperatures, it quickly reverts chemically to the preferred dihydrate form, while physically "setting" to form a rigid and relatively strong gypsum crystal lattice: This reaction is exothermic and is responsible for the ease with which gypsum can be cast into various shapes including sheets (for drywall), sticks (for blackboard chalk), and molds (to immobilize broken bones, or for metal casting). Mixed with polymers, it has been used as a bone repair cement. Small amounts of calcined gypsum are added to earth to create strong structures directly from cast earth, an
Blackboard Inc. Engage. In March 2012, Blackboard acquired Moodlerooms Inc. and NetSpot of Adelaide, Australia, which then became the basis of Blackboard's Open Source Services division. From January 2014 to April 2015, Blackboard acquired nine companies, including: MyEdu, an Austin-based online education company; Perceptis, a provider of help desk and administrative services; CardSmith, a company that offered cards for student ID and on-campus payments; Requestec, a provider of technology for VoIP, video conferencing and instant messaging; and Schoolwires, a company that specialized in building school websites. In August 2015, Blackboard acquired Colombia-based Nivel7, possibly the largest Moodle services provider in Latin America.