Different stages and types of gold if you like: Concentrate, the results of passing your materials through the dredge.
Visible Gold: exactly what it says, wash the concentrates first, or pan it if you like into another container, whats left in the pan is visible gold.
Next stage: Whats left in the container Dry, pass through 3 different fine mesh filters. The largest size wash and extract FINE gold add residue to next size, wash and extract FINE gold, add residue to 3rd and smallest material and wash and extract FINE gold. What remains NOW is POWDER gold, IRON Pyrites Possible Lead and REES.
Now you can use a Magnetic Centrifuge to extract the Iron.
What you are left with now is POWDERED GOLD and REEs.
I must stress that we never had Magnetic Centrifuge and were never interested in REEs. and would dump iron, powdered gold and what is now called REEs back into the river.
Some old boys would sit with a plastic bucket with water and the DIRTY as we called it and a use a Speaker Magnet in a plastic bag to extract as much Iron as poss. Then use a tort or and or nasty chemicals to get the gold when they had stockpiled enough.
What I know about REEs you could put on the back of a postage stamp.
There are more advanced methods than above but I have tried to explane the process.
Hope this helps
Dredgemaster