Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate.
Gypsum is processed in five stages:
- Excavation is carried out by digging out an area of ground where the gypsum is located using open-cast techniques. To reach deeper deposits drift or shaft mines may be needed.
- Crushing the gypsum rock, especially if subsequent heating is to be done in a pan rather than a shaft kiln. Crushing should reduce the gypsum to grains of less than a few millimetres across.
- Screening with a sieve will remove large grains which have not been crushed properly which may contain impurities.
- Grinding if the gypsum is to be used for high quality plasterwork or for moulding, medical, or industrial applications. The relatively soft gypsum could be pulverised in agricultural mills.
- Heating by using a rotary dryer to dewater the materials, and a cyclone collector to gather the final gypsum powder for final application.