Mining and Using Minerals - When you buy a roll of aluminum foil or some baby powder, do you think about how the products were made? Probably not. We take many everyday items that are made from minerals for granted. But, before the products can be put on store shelves, minerals have to be removed from the ground and made into the materials we need. A mineral deposit that contains enough minerals to be mined for profit is called an ore. Ores are rocks that contain concentrations of valuable minerals.
Finding and Mining Minerals
Geologists need to find the ore deposits that are hidden underground. Different geologic processes concentrate mineral resources. They study geologic formations searching for areas that are likely to have ore deposits. They test the physical and chemical properties of soil and rocks.
For example, they might test rocks to see if the rocks are magnetic or contain certain chemical elements. Then, geologists make maps of their findings to locate possible ore deposits. Today, satellites do some of the work for geologists. Satellites can make maps of large areas more quickly than geologists on the ground can.
After a mineral deposit is found, geologists determine how big it is. They also calculate how much of the valuable minerals they think they will get from mining the deposit. The minerals will only be mined if it is profitable. If is profitable to mine the ore, they decide the way it should be mined. The two main methods of mining are surface mining and underground mining.
Surface Mining
Surface mining is used to obtain mineral ores that are close to Earth’s surface. The soil and rocks over the ore are removed by blasting. Typically, the remaining ore is drilled or blasted so that large machines can fill trucks with the broken rocks. The trucks take the rocks to factories where the ore will be separated from the rest of the rock. Surface mining includes open-pit mining, quarrying, and strip mining.
Placers are valuable minerals that have collected in stream gravels, either modern rivers or ancient riverbeds. California’s nickname, the Golden State, can be traced back to the discovery of placer gold in 1848. The gold that attracted would-be miners from around the world weathered out of a hard rock, travelled downstream and then settled in a deposit of alluvium.
The gold originated in the metamorphic belt in the western Sierra Nevada, which also contains deposits of copper, lead zinc, silver, chromite and other valuable minerals. Currently, California has active mines for gold and silver, and also for non-metal minerals like sand and gravel, which are used for construction.
Underground Mining
Underground mining is used for ores that are deep in Earth’s surface. For deep ore deposits, it can be too expensive to remove all of the rocks above the ore. Underground mines can be very deep. The deepest gold mine in South Africa is more than 3,700 m deep (that is more than 2 miles)! There are various methods of underground mining. These methods are more expensive than surface mining because tunnels are made in the rock so that miners and equipment can get to the ore.
Underground mining is dangerous work. Fresh air and lights must also be brought in to the tunnels for the miners. Miners breathe in lots of particles and dust while they are underground. The ore is drilled, blasted, or cut away from the surrounding rock and taken out of the tunnels. Sometimes there are explosions and sometimes mines collapse as ore is being drilled or blasted.
Mining and the Environment
Mining provides people with many resources they need, but care needs to be taken to reduce the environmental impact of mining. After the mining is finished, the area around the mine is supposed to be restored to its natural state. This process of restoring the natural area is called reclamation. Native plants are planted. Pit mines may be refilled or reshaped so that they can become natural areas again. They may also be allowed to fill with water and become lakes. They may also be turned into landfills. Underground mines may be sealed off or left open as homes for bats.
Mining can cause pollution. Chemicals released from mining can contaminate nearby water sources. The United States government has standards that mines must follow to protect water quality. It is also
important to use mineral resources wisely. It takes millions of years for new mineral deposits to form in Earth, so they are nonrenewable resources.
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