Text Box: Gold Fever !!!! Text Box: Page 5 Text Box:        Gold Recovery in Placer Mining Operations By ICMJ                                     Continued from last month:    This is true in the gold-panning process as well, but a fourth type of particle is also involved.  Very rough or jagged gold particles, flake gold, and float gold will not separate satisfactorily in a gold pan filled with a large amount of heavy material unless the panning is done in a certain manner.  Surprisingly, most of the finer gold will separate because it moves between the heavy particles and reaches the bottom of the pan.  Concealment of gold particles in a gold pan by heavy black sands is called “masking,” and unless it is detected immediately, it could be very misleading.     The best panning method to eliminate masking by black sand is one in which smaller quantities of material are panned at a time, and the material panned carefully to the point where there is only black sand remaining.  Then, while slowly washing away the black sands, tap the pan steadily with the flat of one hand on the side where the black sand is located, close to the center of the pile.  The gold particles, being heavier, will “walk” out from the heavy material towards the area you are tapping.     Use of this method is very important when panning down concentrates, as masking of values can sometimes amount to fifty  or sixty percent—and you would never see it.  To check the pan recovery, repan the waste material several times.  If you still find gold by repanning, tap harder or pan less concentreates each time.     Another way that values are lost is when a magnet is used to extract black sand.  Where the concentrate is heavy, or the gold particles are flat or rough, the particles remain suspended in the material.  When the magnet is used, it picks up any suspended gold along with the magnetic sand.  This is because the lines of force on the magnet pick up magnetic material under the gold particles, and lift them out of the pan.  This can be proven by panning the magnetic sand after it is extracted.  In a heavy concentrate, use of a magnet can remove up to 75 percent of the gold.     Also important is the fact that platinum is slightly magnetic, and is often alloyed with iron.  Use of a magnet would remove most of the platinum group alloys, also.  There are instances reported of platinum group metals having been alloyed with 11 to 15 percent of iron by volume.     All waste material and tailings from placer mines should be checked regularly for loss of values occurring during processing.  Magnetic separation should be used only under controlled conditions, and the removed material checked for values.  Any time concentrates are separated by panning, the discarded  portion should be rechecked.  If losses are occurring in  the recovery system, they can generally be corrected by a slight adaption either in method or in equipment. Note “packing” of riffles in this large sluice; gold is likely to be lost        Dilligence keeps this small sluice from “packing”                      

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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