Jigs are continuously pulsating gravity concentration devices. Jigging is the separation of heavy and light particles of a mineral in an ore bed using a medium (air, water or solid). Jigging is used in the separation of, e.g., chromite ore, gold and diamonds, and the process requires few enrichment chemicals.

The jig has two parts: a plunger and a screen. As the plunger moves downwards, the ore bed on the screen rises upwards and, correspondingly, as the plunger moves upwards, the ore bed descends on the surface of the screen. Therefore, as the ore bed opens and closes, the heavy particles sink to the bottom of the bed and the lighter particles rise to the top of the bed.

A Denver jig was in use in the Outokumpu mine.