Coal is highly variable with respect to the physical and chemical properties that affect its use. Industries that use coal specify a range of properties that are required for their intended use. Coal suppliers try to find coals that most closely match those requirements. Coal is treated in processes called preparation, beneficiation, cleaning, and/or processing ( they all mean the same thing) to prepare a material that meets the customer's needs and is as homogenous as possible. A preparation plant will have a variety of technologies designed to separate coal from the rock it is mixed with when mined. Preparation plants are usually constructed as near as possible to the location where the coal is mined, although a single plant may service multiple mines in an area.