Correct Response: C. These techniques are used where small particles of precious metal ores are mixed with sediments in a stream. A slurry from the stream sediment is agitated in a pan with water running over it. The ores sink to the bottom of the pan due to higher density while the rest of the sediment is washed over the top edge. Buoyancy (A) is not a factor since most if not all of the particulates are denser than water. Particle size (B) is not a factor since the particles are not passed through a sieve. Melting point (D) is not a factor since the entire process is carried out at ambient temperature, which is far below the melting points of any of the materials involved.
