Gold originates in several mineral and rock formations.
Prospecting for gold is a risky yet exciting activity for the adventurous entrepreneur. A bit of luck and a lot of searching can uncover enough precious metal to ensure an early retirement. If you want to prospect, learn about the mineral and rock formations that produce gold. Gold originates from several different sources, each of which requires different methods and tools for mining.
Lode Deposits
Lode deposits are found within solid rock formations. Traditionally, a prospector would hit rock with a pick until he reached the lode. However, pure gold nuggets are found very rarely. More often, the deposit consists of other minerals such as quartz, calcite and pyrite. These deposits are found in several types of geologic formations. In places such as Nevada, active geothermal systems below the Earth's crust create veins of gold-enriched metal within fault zones. Another source is gold-bearing solutions that are expelled from magma as it cools. A third possibility involves deeply buried sedimentary and volcanic rocks that turn to gold under enormous pressure and temperatures.
Placer Deposits
Placer deposits require the prospector to pan for gold crystals along a stream. Look for these deposits in places where coarse sands and gravel have accumulated, such as inside bends of rivers and streams as well as areas downstream from large outcrops of bedrock or large boulders. Black sands also are a good place to find gold and even some gemstones. As with lode deposits, placer deposits are created by geothermal heat. Magma or hot water liquefies the gold, which causes it to rise to the Earth's surface. At that point, erosion detaches it from rock, and it often ends up flowing in crystals downstream into the prospector's pan.
Low-Grade Disseminated Deposits
Since 1980, low-grade disseminated deposits have become an increasingly important source of gold. In these deposits, microscopic particles of gold are often hosted in sedimentary rocks such as limestone or dolomite. Many of these deposits lie along a few geologic trends in Nevada. Gold must be extracted from these deposits through a chemical process such as cyanide leaching. While the ore grade of these deposits is high, the particles are so small that metal detectors cannot find them and they eluded independent prospectors until very recently.
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