There are two: strip mining and underground mining. Strip mining involves completely digging up the ground, layer by layer, until nothing remains but a crater. Underground mining involves digging a network of tunnels deep underground, and is less disruptive to the native wildlife but can cause sinkholes and disturb the flow of underground water, as well as create risk of cave-ins killing miners.
In terms of the count, by commodity, sand and gravel quarries and stone quarrying operations undoubtedly constitute the greatest number of facilities. In the US crushed stone, sand and gravel, and cement are three of the 6 most valuable mineral commodities produced. There are more than 6500 sand and gravel quarries, and more than 4000 stone operations in the US.
Click here to cancel reply.
Sorry,At this time user registration is disabled. We will open registration soon!
Don't have an account? Click Here to Signup
© Copyright GreenAnswers.com LLC