Patent for an "improved method of and apparatus for treating mineral pitch and similar material to readily separate the asphalt and asphalt-oils from sand, bituminous rock, and other impurities contained in the mined material and removing the sand and impurities" (lines 12-17). The method circulates the material in hot water to separate the asphalt and asphalt-oils from the sand and impurities. The asphalt and oil rise to the top of the water and the impurities sink.