Gypsum

Gypsum mineral is heated to produce materials useful for building. It is a soft sulphate mineral composed of calcium sulphate dihydrate (CaSO4·2H2O) commonly found in sedimentary rock. Its water content is essential to its unique properties. When heated it undergoes a process of calcination, whereby it gradually loses its water content. This yields a very cheap material suitable for building products, such as board, plaster of Paris and stucco.

It is soft and easily scratched, and naturally bright white, like the White Sands Desert, New Mexico, which is an incredible gypsum dune field. Colours are the result of impurities. As well as building products, gypsum is used in agriculture for soil conditioning and as a fertiliser, concrete making, dental moulds, casts for broken bones and sculpture, for example.

Gypsum is recyclable and new plasterboard panels typically contain a proportion of recycled material. Sources include construction waste and unused boards, and post consumer waste from renovation and demolition work. While pure gypsum can be recycled indefinitely, contaminated waste is less straightforward and care must be taken to ensure the fire performance of new products made of recycled material is not compromised.