US Patent 7845498 Separation of metals from sand

The present invention provides a method and an apparatus for removing heavy metals such as gold from sand. A mixture of sand and metals is placed in a hollow tube which has an open end, an opposite closed end at a relatively lower position, an exterior, and an interior formed into spiral grooves. The grooves are arranged in a helical fashion so that metal caught in the grooves is carried toward the open end of the tube as the tube is rotated. Water is supplied to the tube to mix with the sand and metal, so that rotation of the tube causes relatively heavy metal to be washed from the sand and water mixture into the grooves. The mechanism can be transported to a location where heavy metals naturally occur in sand or other materials.