Comparison of the Wilfley concentration table and hand panning for concentration of heavy minerals prior to geochemical analysis

Chemical analysis of heavy—mineral concentrates of stream sediments is a common geochemical exploration technique used by the U.S. Geological Survey. Generally these concentrates are prepared by hand panning at streamside or in a washtub and then further concentrated using heavy—liquid (bromoform) techniques in a laboratory. Concentration using heavy liquids is slow, tedious, and expensive for large surveys such as mineral evaluation of wilderness areas. In addition the cost of bromoform is expected to increase greatly because most if not all chemical companies in the United States have ceased production of the compound due to problems in meeting the safety standards of the U.S. Environmental Protection Agency (E.P.A.). Preliminary studies by the E.P.A. suggest a severe health hazard may be incurred by inhaling vapors of or contacting the skin with chemicals like bromoform. Heavy—liquid concentration of thousands of heavy— mineral samples carries an unavoidable risk of exposure to bromoform. The risk, expense, and time required by routine heavy—liquid concentration of heavy minerals should be eliminated by finding other methods to satisfactorily concentrate minerals whenever it is possible.

Heavy—mineral concentrates can be used in several ways in geochemical exploration and each way has certain standards for the nature and quality of the mineral concentration required. The nature of the concentration refers to whether the heavy minerals are analyzed in bulk or whether they are split into magnetic fractions using a hand magnet and possibly a Frantz Isodynamic Magnetic Separator.