Evaporites consist of soluble salts that have been deposited by evaporative processes. They include a wide variety of chemicals and are often interlayered with other sedimentary material. Because of their solubility, those deposits that are not in deserts, are underground.
Evaporites are an extremely important mineral resource. They require specialist mining techniques. Underground mining is frequently constrained by limits on subsidence in which case bord and pillar operations are used. Occasionally, deposits can be mined by longwall techniques where a goaf area is created. They may also be mined by solution processes.
One of the characteristics of evaporites is that they creep under load. Determining this level of creep is important in the design of underground mines as it can change opening sizes and redistribute stresses. Determining the rate of creep of evaporites requires special testing.
The creep behaviour of evaporites may be used to deliberately seal toxic wastes into evaporite deposits. Openings are created in evaporites that are under sufficient stress that they creep and seal up. This has to be carefully managed so that sudden collapse of these openings does not occur.