After the gold-bearing ore has been crushed, grinded and milled, a dark grey powdery substance is achieved. In it, there's gold particles!
You can't see them but they're there combined with other stuff, the point of this stage of the journey is to separate and concentrate the gold from the rest.
Gold is usually heavier than other substances so it will fall to the bottom when in water, mixed with oth
er materials. This is how shaking tables take advantage of this property and use gravity to help, hence it's called a method of gravity concentration (because gold settles faster than other minerals). As the deck shakes or vibrates, gold particles concentrate on one side of the deck while midlings and tailings separate on the other.
These tables are slightly tilted with raised ridges. The finely crushed ore is fed from one end of the table along with water and as it travels along the vibrating table this movement is helping separate the gold particles. Special grooves in this table trap the sinking gold and direct it to collection points as lighter minerals are washed away.
Shaking tables provide high grade concentrates and liberated gold, although they are expensive and require professional operators. 
The fine particles of gold are captured and washed before the next stage, recovering the gold through smelting.
In the next post, see how fire transforms gold powder into partially-refined gold.
Top Photo: © Desirée Binternagel, Fairever.
