Gold - Part I
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Forced up from deep inside the earth riding a jet of superheated water surrounding a core of hot liquid rock, untold riches have been deposited in cracks and fissures near the surface of the Earth, waiting for someone to find them. Precious metals are hidden deep in the bowels of the mountains. Gold, silver, platinum, and others have all been deposited in mountains all over the world. Each process that deposits these metals is at the same time unique and surprisingly the same. As an example, we are going follow the processes that deposit gold.
Gold is a very interesting metal; it is one of the few metals yellow in color. Gold has physical properties that make it very desirable to people. First, it is pretty. People have liked the glimmer and shine of gold for longer than recorded history. Second, it is malleable. Malleable means that it is easy to shape. Third, it is ductile. Ductile means it can be stretched into a thin sheet or wire. Fourth, it conducts electricity.
A deposit of gold is a concentration of gold in the same area or in the same rock formation. Gold miners really like gold deposits and work really hard to find them. There are two main types of gold deposits: Primary deposits, and Secondary deposits. There is a third type of gold deposit that geologists do not fully understand. It is called the Carlin-type gold deposit and is named after the first miner that found it.
Primary deposits are concentrations of gold inside rock. There are two main types of primary gold deposits. The first type is lode deposits. Load deposits are formed by the same type of events that form mountains. Here is how it happens: When the earth’s plates crash together they pile up on top of each other and form mountain ranges. Sometimes extremely hot water is forced up from deep inside the earth. The extremely hot water flows up through the cracks in the rocks. These cracks are called faults. The water contains lots of minerals and elements. As the water travels through the rock, it cools down. As the water cools it cannot hold onto the minerals. The minerals “fall out” of the water and are deposited along the cracks and fissures in the rock. Gold and quartz are often found together because they both get deposited in cracks in the rock though this process.