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
Vezo people catches that men bring them. With what they earn, women buy rice, the staple food, other essential foodstuff and a variety of luxury items. Children go to school in the one village school building, where there are two designated teachers. However, due to the deterioration of public administration in Madagascar, the building and the teachers are hardly ever occupied. Whenever children are in the building, and if the teacher has not run out of chalk, the teaching largely consists in copying letters, numbers, and short sentences from the blackboard onto the child's own A5 size blackboard. Understandably, the many children