Types of Gold Deposits

1. 
   colorful mineral deposits image by emu from Fotolia.com
   Gold deposites form in different ways.
   Gold mining is an ancient industry. The gold used to make artifacts from Egyptian tombs and temples dated to over 5,000 years ago came from deposits in the Upper Nile region and the Nubian Desert. These deposits supplied gold to most of the Middle East.
   
   Gold miners use ingenious methods to mine gold deposits. The ore can be found on the surface where erosion washes it into streams, in lodes near the surface and inside rock formations deep under the earth.

   Placer Deposits

2. 
   batée 02 image by thierry planche from Fotolia.com
   Panning is a type of placer mining.
   When you think of gold mining the image of Gold Rush miners standing in a stream swirling water around in pie pans often springs to mind. The people infected with gold rush fever rushed to California to exploit placer deposits of gold.
   
   Placer deposits are formed by erosion of rock over time. The first discovery of gold over 5,000 years ago in Mesopotamia was likely the accidental find of a placer deposit. Over time weathering by wind, water and temperature changes crumble the ore bearing rock into particles.
   
   According to the University of Alaska Geophysical Institute, gravity carries the gold ore and weathered rock down slope where the gold accumulates. The gold, being heavier than the rocky particles and sand, moves down more slowly than the lighter particles which are washed away. (See reference

   Intrusion Related Lode Deposits

3. 
   raw quartz image by FotoWorx from Fotolia.com
   Gold is often found in quartz formations.
   Gold is formed underground by the process of precipitation. Many of the gold deposits occurred along with the formation of quartz. Lode gold deposits can occur as a result of water seeping down into the earth.
   
   According to the U. S. Geological Survey there are several hypotheses on the origin of gold. One widely accepted theory involves the circulation of ground water. Water from rain or other sources seeps down into the earth until it reaches deep areas heated by magma.
   
   Under high pressure the heated water absorbs minerals from the surrounding rock. As the water gets closer to the surface it gets cooler, causing the minerals, including gold, to precipitate out of the water forming veins of gold bearing rock. (See reference 2)

   Volcanic Gold Deposits

4. 
   magma image by Svetlana Romanova from Fotolia.com
   Cooling magma can precipitate gold deposits.
   According to the U.S. Geological Survey most of the minerals mined on Earth are associated with magmas found deep within the roots of extinct volcanoes. The heat melts the rocks and circulates the minerals, including gold, up to cooler regions where the magma solidifies instead of erupting.
   
   The heat of the molten rock allows the trace amounts of gold and other minerals to become concentrated. When the rock cools minerals precipitate out and accumulate into ore deposits around the hardened magma. (See reference 3)