Mining

This 156-ounce gold nugget is the largest found in California. It was discovered by a lucky prospector using a metal detector. Perhaps you have seen someone use a metal detector at a park or at the beach—walking around scanning the ground for coins and other treasures. Finding a gold nugget like this is extremely lucky and quite rare.

Most gold and other economic minerals are found, not by luck, but by knowing where to look to find them. Gold, for example, can be found in areas affected by hydrothermal metamorphism, as you read about in the Rocks and Minerals Unit of this course. Once we identify suitable environments, we carry out in-depth investigations to see if any mineral ores exist in the area. An ore is an area of rock that contains enough of a certain mineral to be worth the cost of extracting it out of the ground and selling it. Mining is the process whereby rock and mineral resources are extracted from the ground and processed out of the ore.

Suppose you find a golf ball-sized gold nugget in your backyard. Have you found gold ore?
 

While a gold nugget that size would definitely be economically profitable to you, it would not necessarily count as ore. To be ore, there has to enough gold in your yard to financially justify digging up your entire yard, turning it into a mine, and then being able to extract gold from it for years and years.