1. Introduction to the extraction of METALS

What methods can be used in extracting metals from mineral ores?

The Earth's crust contains many different rocks.

Rocks are a mixture of minerals and from some we can make useful substances.

A mineral can be a solid metallic or non–metallic element or a compoundfound naturally in the Earth's crust.

Mineral ores are naturally occurring rocks that provide an economic starting point for the extraction and manufacture of metals for a huge variety of purposes ie a metal ore is rock containing sufficient metal to be worth extracting the metal from it.

The simplest definition of an ore is a mixture of a metal containing mineral and other materials ('minerals') from the surrounding rocks, which can be described as impurities with respect to what you want from the ore.

Metal ores are obtained by mining and that this may involve digging up and processing large amounts of rock.

Most ores are mined have to be concentrated before the metal is extracted and purified.

This often results in lots of waste material that must be dealt with from an environment of view.

The social, economic and environmental impacts of exploiting metal oresare discussed on a separate page.

The rock must CONTAIN enough of the metal compound, hence enough of the metal, to be worth exploiting the ore reserve and extract the metal by physical and chemical processes.

Low grade ores are usually uneconomic to mine and process, but high grade ores have a high enough metal content to be worth mining and extracting the metal.

The metal ore, a mineral or mixture of minerals from which economically viable amounts of metal can be extracted, i.e. its GOT to have enough of the metal, or one of its compounds, in it to be worth digging out!

Ores are often oxides, carbonates or sulphides because these non-metals readily combine with many metals.

e.g. iron  +  oxygen  ===> iron oxide ores

Fe  +  O2(air)  ===> Fe2O3 or Fe3O4    (not balanced equations, just the idea!)

This the typical chemistry involved in metal ore formation.

In extracting metals from ores you have to reverse the process e.g. by heating the ore with carbon (coke or CHARCOAL) in a very hot smelting furnace e.g. in a blast furnace to make iron ...

iron oxide ore  +  carbon  ===> free iron  +  carbon dioxide waste gas

Fe3O4  +  2C  ===>  3Fe  +  2CO2

The iron oxide is reduced (oxygen loss) and the carbon reducing agent is oxidised (oxygen gain).

This is typical extraction chemistry for less reactive metals.

These ores are all FINITE resources so we should use them wisely!