Copper
I don't know about the rest of you, but I had no idea how you would mine copper. I expected it to be quite simple with a bunch of machinery, but really there are a lot of different processes and techniques that can be used. I did a little bit of research and came up with some interesting tidbits and a couple processes which I briefly describe.
First off some interesting facts about Chile today: Chile has about 24% of the world's copper reserves, and Chile's mine, Codelco, is the world's tope copper producer. In 2010 Chile produced 5,390 metric tons of copper.
Copper Mining:
There are various copper extraction techniques which I'll give a brief overview of.
The first stage: the rock containing copper is crushed into small particles. This process is called accurate grinding or comminution. The particles are then separated to remove the gangue (minerals such as silica, magnesia, alumina, and limestone), then by physical liberation where the ore minerals are separated from the rock.
If the copper ores are an oxide ore: then a hydrometallurgical liberation process is undertaken. Big word, yes, but actually isn't that difficult to understand. Hydro - means water. So pretty much this extraction uses aqueous chemistry to recover the metals from the ore. This is only possible because of the soluble nature of the minerals.
If the copper ores are sulfide ores: a froth flotation process is used. This is a modern technique that was invented in the early 1900s in Australia. The froth flotation is a complicated process - in a nut-shell depending on the ore different "frothers" are used in order to bring the ore to the top of the cell which is then pumped out. If you are interested in the chemistry of it - go look it up!
This is a copper sulfide foam in one of the froth-flotation cells.
This is an example of what a froth-flotation cell would look like. It takes special machinery, which is why many jobs were lost in Chile as this took over.
After the ore has been removed the copper sulfide is smelted. The purpose of smelting is to eliminate the unwanted parts such as iron, sulfur, and the gangue minerals. This produces a matte. Now they would have copper sulfide. The sulfur is then removed at a high temperature as sulfur dioxide by blowing air through the molten matte.
For all you chemistry people out there here's the equation.
2CuS + 3O2 ---> 2CuO + 2SO2
CuS + O2 ---> Cu + SO2
It is then refined in a furnace or by electrolysis.
And...this is only part of the process of refining copper from ore. Hopefully this blog gives you a little insight into copper mining and how complex it is!