how do you seperate gold from other rocks, dirt and so on?

Answer 1

Gold is much denser than rock, so if the ore is broken up, most of the rock particles can be removed by exploiting their lower density. This might be in water washing cyclones, which are conical devices where a suspension of ore and gold is pumped in at one side at high speed. The suspension whizzes around inside and the denser materials tend to fall through the point of the cone while the less dense, rock in this case run out at the top. This is just one of many such devices that may be used. Manual methods included the pan and the cradle
http://www.goldgold.com/panninginstructions.htm

http://www.goldcradle.com/history.html


Other methods might include froth flotation where very fine particles are mixed with an oily material, pine oil was once used, and a lot of tiny air bubbles are introduced at the bottom by a specially designed stirrer. The gold and perhaps other metal ores like copper (which is often found in some gold bearing rocks) in this system may associate with the bubbles and oil and foam over the top of a bath, while the rock particles are preferentially wetted by water and are taken out the bottom as mud.

These two methods and others may be used in different places but all produce a concentrate which them may be treated with mercury or sodium cyanide. Mercury dissolves gold rapidly, leaving rock behind. The solution of gold in mercury then passes to stills where the mercury is distilled off for re-use, while the gold is left behind.

I don't know exactly how the cyanide process works, but it is applied to very fine rock particles and has been in use since the 19th century.

http://en.wikipedia.org/wiki/Cyanide_process

http://en.wikipedia.org/wiki/Froth_flotation

http://www.natcogroup.com/Content.asp?t=ProductPage&ProductID=76

Answer 2

Panhandlers separate gold mechanically by swishing a mix of dirt and gold flakes or nuggets in a pan filled with water. The gold is very dense and stays in the pan while the lighter dirt is rinsed away.

Answer 3

Miners use simple panning. Based on the fact that gold is extremely dense

Answer 4

Usually by weight or by breaking the ore up small and dissolving the gold with nasty arsenic or mercury then getting the gold back out of solution.
http://www.britannica.com/ebi/article-201603