How is Aluminum Mined?

January 13, 2021

How is aluminum mined?

  1. Locating bauxite ore
  2. Site preparation
  3. Mining of bauxite
  4. Processing of bauxite

Aluminum is one of the most abundant materials on Earth. In fact, it makes up around 8% of the earth’s crust, despite not being a naturally-occuring one. With the many properties of aluminum — i.e. lightweight, malleable, ductile, non-corrosive, and long-lasting, you’ve probably asked yourself “How is aluminum mined?” The process is definitely complex and involves numerous phases before aluminum metal can be fabricated into slugs, billets, ingots, blooms, and the like. 

Aluminum mining can be classified according to the following processes: locating bauxite ore, site preparation, mining of bauxite, processing bauxite, and processing of bauxite. The entire technique for extracting aluminum out of the Earth’s crust doesn’t just concern with the quality of the mining and the drilling. Like all other ores, there should be a consideration for site safety and sustainability. Continue reading to learn more. 

Locating Bauxite Ore

An open-pit bauxite mine

As mentioned before, aluminum metal does not naturally appear in nature, but rather it is mined as an ore called bauxite. The bauxite ore is classified as a sedimentary rock that appears as reddish and clay-like — which seems to be a far cry from the appearance of aluminum once it has already been processed and fabricated.

One important thing that should be understood is that the bauxite does not contain 100% aluminum or alumina. The figures may vary and the contents can range from as low as 30% of the material, to as high as 50%, depending on the quality of the rock. This is due to the fact that bauxite ores are also composed of other aggregates, different types of iron oxides. There are also traces of phosphorus and zinc that can be found in a single ore.

Bauxite ore deposits can be found in large reserves in subtropical and tropical regions like Africa, Australia, South East Asia, East Asia, and South America. Australia ranks number one in bauxite ore production which is at an estimated value of 25.4%. They’re followed by China and Australia which have 23.7% and 17.0% respectively. Although despite this, Guinea is still at the top spot of bauxite ore reserves — more than 7 million metric dry tons.

Site Preparation

Before the mining process takes place, there should be site preparation in order to make sure that the mining activities don’t disturb any ecological sites. This is usually done in coordination with mining geologists, miners, environmental coordinators, surveyors, engineers, and the like. 

The professionals mentioned above all collaborate together to ensure that the mining process does not create harmful disruptions on the land. For example, the miners would be handling the right kind of mining equipment like excavators and scapers. Geologists would be mapping out the location of the reserves. This is done by identifying the type of flora and fauna present and making sure that the bauxite ore mining activities do not have harmful impacts on the environment. 

All of these activities are overseen by a manager who ensures everyone is following health and safety guidelines and are working according to the mining laws and regulations in that site. 

Mining of Bauxite

A piece of raw bauxite ore

After the planning phase, bauxite mining can already begin. Although there may be other mining methods that may be used, the most ideal is open-pit or surface mining. As the name suggests, this method does not involve underground activities. 

With the help of heavy machinery and surface mine blasting, miners would begin isolating the bauxite ores from the land surrounding them. This is called land clearing and its purpose is to free or loosen up the compacted soil that may be covering up the ores. 

Excavators or large-sized shovels would then be used to collect the soil layer where most of the bauxite ores are located. These are then transferred onto conveyor belts that load them onto a truck before transporting the soil to a processing plant or ore refinery factory. There may also be cases wherein the ore has to be crushed in order to create finer aggregates to allow for easy transport. 

Processing of Bauxite

Once in the refinery plant, the bauxite ores are not ready for further processing. Simply put, this process involves purely extracting the alumina compound from the ore. This is done through the Hall-Heroult process (also known as smelting) and the Bayer process.

In the Bayer method, the refining technique focuses on collecting the aluminum oxide or alumina from the ore. This is a hydrometallurgical technique wherein the crushed ores are dissolved into a caustic solution or a caustic soda in hot temperatures. What this does is to eliminate the other unwanted materials from the ore (iron oxides, crystals, and other aggregates) in order to create a sodium aluminate solution.

On the other hand, the Hall-Heroult process relies on a smelting technique. Here, the ores are mixed with another solution — either calcium fluoride or sodium aluminum hexafluoride which deposits pure aluminum afterwards. This creates an electrolytic reaction involving a cathode and an anode. The aluminum metal will be deposited to the cathode at the end of the process, while hydrogen will be deposited at the anode.

Key Takeaway

By now you can probably answer How is aluminum mined?” The entire process starts with locating the bauxite ores. Then the site will be prepared for drilling, blasting, and mining of the ores. The crushed bauxite ores are then transferred onto a conveyor belt which loads the materials into a truck for further refining at a factory or plant.

Once the aluminum has been successfully extracted from the ores, they can now be casted into billets, ingots, or slugs. These will then be useful in manufacturing various aluminum products and profiles that can be used structurally and decoratively.