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The next unit operation involves the removal of materials that are heavier than the beans. This is a complex operation designed primarily for removing stones and mud balls, which are a result of the harvest. The use of a gravity table provides a large surface area with vibrating mechanical force to remove these heavier materials. This shaking action and the slight incline of this gravity table impart greater energy to the denser stones or mud balls. Because of the density differences, the heavier materials proceed to move up the incline and are segregated over the edge of the table.

In the gravity separator, a large volume of dry beans is spread in a very thin layer and continuously moves over the gravity table. As this table rapidly shakes, it sorts the stones and mud balls and allows the beans to pass forward. The stones and mud balls are separated from the dry beans and are collected in a waste disposal bin. Stones and mud balls are characteristic of the geophysical structures within the bean‐growing region and may vary in size, shape, and density.