A simple appliance used in the search for gold and other heavy minerals. By means of water washing, the lighter, worthless material is separated from the valuable, heavier minerals, which are made visible by concentration and retention in the dish. Standard dishes with sloping sides are made in sizes ranging from top diameter 10 to 18 in (25 to 46 cm) and from 2 to 4 in (5 to 10 cm) deep, with riffles or grooves to retain the heavy minerals.