For the forces of nature to separate out gold from hot magma, it helps to have swirling magma and pools of underground swirling water working together. To trap and build up the gold deposits, we need to have gold-bearing fluids that rise off the magma seep into cracks and fissures in the earth. This is somewhat analogous to the way a miner sloshes increasing concentrations of "black dirt" carrying gold towards the bottom corner of a pan. It also helps to have types of rock whose molecular structures tend to grip and hold gold particles, which are typically sedimentary rocks. Lastly, it helps to have nice long channels of seepage where under various temperature and pressure conditions, the different elements within the gold bearing fluids start to condense (mineralize) and sort themselves out and form distinct deposits at different intervals. As an example, as gold bearing fluids simultaneously push up diagonal crevices and cool down, the base metals start to precipitate out first, starting with cobalt, and then followed by lead, zinc, and copper. Further up the crevice, we get arsenic, mercury, antimony, and gold. This is one reason why elevated arsenic, mercury, and antimony concentrations in soil can be a clue regarding nearby gold.
