FINDING GOLD

Almost all alluvial gold is found in small nuggets, some so tiny that they are more often called gold dust. The largest nugget ever recorded weighed 200 pounds and was found in Australia, where it was named the "Welcome Stranger."

Since this gold is usually found in or near water, water is used to find it, taking advantage of the fact that the gold is so much heavier for its size than the rocks, gravel, and sand with which it is found. The method is called panning. The Nubians and Egyptians "panned" with animal skins or cloth, which may also account for the "golden fleece" of legend. The method, nevertheless, is the same.

Gravel and water are scooped into a pan. As the pan is shaken and the water poured off, the gold nuggets and dust settle to the bottom while the nonprecious minerals are washed away. In Colombia in South America, where gold is still mined using this principle, huge dredges have replaced hand panning. Another name for this kind of gold is placer gold, and panning is called placer mining. Sometimes mercury is used, since gold sticks to mercury. When the two metals are heated, the mercury vaporizes and leaves the gold behind.

The gold found deep in the earth is native gold. Because it is found with silver, quartz, and other minerals-minerals that have been washed or eroded away in alluvial gold-it is generally less pure than alluvial gold. As a result, the ore must be crushed, smelted, and refined to melt out the pure gold.