xeyla

Originally Posted by waldronate

A lot of economically important minerals (lead, copper, silver, gold, tin, zinc, etc.) are associated with hydrothermal systems, as are many types of gems (beryls like emeralds, oxide gems like sapphires, and silica gems such opals are commonly formed in hydrothermal systems; diamonds are not).

Hydrothermal systems come in a number of forms, but the basic idea is that hot water dissolves out soluble things like the common metals and sulfur in the hot areas and deposits them in cooler

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Originally Posted by Adversary

Gold is usually found with quartz (but unfortunately not the other way around) and granite which is are igneous materials so there would have to have been some magma near the surface of the earth. I have also heard that some gold was found in meteor impacts but I can't believe that would be a major source.

Marble on the other hand is metamorphosed sedimentary rock high in carbonates (think limestone). The original limestone was formed on a seabed with lots of shell forming creatures.

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