How a Gold mine is Created

An open pit gold mine.
Photo by Patrick Huber

A recent question that was posed to the author on www.allexperts.com was how a gold mine came into being.  The questioner realized that a gold mine is usually large, but how they came into being just eluded him.  He thought spelunkers, cave explorers, discovered the gold minerals while exploring the cave.  A few working gold mines probably were discovered this way.  Most gold mines are purpose dug excavations with three types of gold mines that are recognized.  The people that develop a gold mine are called gold mine developers.  Although it is nothing more then a large construction job there are enough differences so sometimes this is a specialty in the construction industry.

A gold nugget from a placer mine.
Photo by Rob Lavinsky

The first of these gold mines is the placer gold mine where through the process of weathering the valuable gold minerals are released from the bedrock that encloses them.  Most of these deposits find their way through the process of soil creep to an ocean or river where they are found in the bedload mixed with many other lighter gold minerals.  Another type of gold mineral deposit found is the result of weathering in place.  The deposits are usually found in the tropics between 32 degrees north and south of the equator.  Many of these are found associated with quartz that remains in place while the other gold minerals are turned to clay around them.  The gold and other gold minerals stay more or less in place waiting to be gold mined.  A placer gold mine is usually limited to gold production although there are exceptions to the rule other placer gold mines also produce tin and rare earth gold minerals.

Entrance to a gold mine adit in Japan.
Photo by PHGCOM

Other gold mines are located in bedrock, and usually are called lode gold mines if they are for mining gold.  Basically there are two types open cast that is nothing other then a large hole in the surface of the earth.  The other type of bedrock is one underground.  Gold mines of this sort are further subdivided by their way of entrance.  One type of gold mine has a shaft going into the ground with tunnels reaching out from the bottom of the shaft.  Some of these gold mines have several layers reaching out from a central shaft.  Other gold mines of this sort have more then one shaft entering the gold mine.  The other type of bedrock gold mine uses an “Adit”  that is a tunnel going more or less horizontal to the surface of the ground.  It costs less to build a gold mine with an adit then one with a shaft.

Headframe of the Oryx gold mine in South Africa.
Photo by Babakathy

Before any gold mine is created there must be lots of preliminary work done first.  Placer gold mines are called “poor mans gold mines” because the preliminary work is often kept to a minimum.  The work can be done by one man or a small workforce.  Bedrock gold mines are for more capital intensive then a placer gold mine sometimes for a truly large gold mine it exceeds 1 billion dollars before any ore is extracted.