Where does metal come from?
Tuesday, 12 April 2022
This might not be what you’re expecting from a metal recycling company but knowing where metal comes from is an key part of knowing why it’s vital to recycle. With perspective on the effort it takes to obtain the materials, we can better understand why finding energy-efficient sources is so important.
In this guide, we’ll show you where certain metals come from and how they might be recycled (you can discover this by clicking on the links within this article).
How are metals found in nature?
Most pure metals come from the earth’s crust. They are found in ores, which is a solid material that minerals and metals can be taken from. Nearly a third of the planet’s mass is the element iron and most of that can be found in the planet’s core. 14% is magnesium, 1.5% is nickel, and 1.4% is aluminium, totalling 49% of the planet. Precious metals like gold, silver, platinum, and palladium, exist only in trace (tiny) amounts.
Vast mining operations, of course, are necessary to extract the most metal ores from the ground. Concentrations of minerals within the rock are often quite low, meaning that a huge amount of excavation is necessary to get the metals. For example, most copper exists in sulphide ores that contain as little as 0.25% copper.
Which country produces the most metal?
Australia and Brazil are currently among the world’s largest iron ore producers. Australia makes up half of the world’s iron ore exports and Brazil exported around 23% of the world’s total iron exports in 2020.
As of 2020, Brazil had reserves of 15 billion metric tons of iron content and 34 billion metric tons of crude ore, producing 400 million metric tons of iron ore in 2020. You can find the latest statistics on this here.
Of course, the metal and scrap metal market are affected by worldwide events. For example, ASM took a look at how coronavirus impacted the scrap metal market.
How are metals created?
Pure forms of metal as we explain, come from the earth. Metals are often divided into ferrous or non-ferrous categories. Ferrous metals contain iron, for example mild steel, carbon steel, and cast iron, non-ferrous metals don’t have iron in them, like copper, aluminium, tin, and lead.
To create metals from ores, they need to be ‘extracted’ and refined. The extraction process may include
- Crushing the ore into powder
- Heating ores at extremely high temperatures
- Using water or a chemical bath to ‘float’ pure metals to the top
- Filtering away impurities
- Applying an electric current to break strong chemical bonds
Refining the ore takes the metals away from their oxides (or other compounds) into the pure form that we need. Here are some of the most common metals and their extraction/refining process*:
The most common ore used for aluminium production is bauxite, a claylike substance. As with iron, getting to the aluminium means getting rid of the oxygen and the minerals in the ore. The bauxite is crushed, then electrolysis is used to split this into aluminium and oxygen then the pure aluminium is cast into blocks known as ingots, which can be worked or shaped or used as a raw material for making aluminium alloys.
Zinc can be produced by a process called froth flotation, which is also used on copper and lead ores. This process involves grinding the zinc ore to a fine powder, mixing it with water, pine oil, and flotation chemicals, and then stirring the mixture to ‘float’ the zinc to the surface. However, smelting is also used to extract zinc at temperatures of up to 1204°C.
Lead ores can be mined from deep underground and is known as lead sulphide as sulphur makes up a substantial portion of the mineral. It’s crushed and mixed with water and uses flotation like zinc to separate it from waste. This lead concentrate needs to be heated to remove more of the sulphur. Sulphur dioxide is an important by-product of the lead refining process, captured and converted to sulphuric acid. Molten lead is around 95-99% pure but commercial lead must be 99-99.999% pure so it is further refined with heat to remove residual copper.
Typically, copper ores contain only 4% copper. At each stage of refinement, the copper gradually becomes more concentrated. The ore is crushed into very small pieces and mixed with water which is pumped into tanks and mixed with air and oily chemicals that help to separate out particles of copper from any other minerals. The remaining ore is then heated in a huge furnace called a smelter, which burns off some of the remaining impurities and leaves a material called copper matte, which is at least 50% copper. Sometimes copper matte is heated with silica and air to remove more waste, leaving a very refined material called blister copper that can be over 97% pure.
Brass is a metal composed primarily of copper and zinc and is man-made. This means, unlike the other metals listed above, it isn’t extracted from an ore, but made from a combination of other metals. Copper is the main component, and brass is usually classified as a copper alloy. To make brass copper and zinc are heated in a furnace until molten, then it is poured into pipes and tubes to solidify. It can also sometimes be rolled into sheets, depending on its final use.
*These are simplified versions of the extraction and refinement process as some can take numerous rounds to achieve the purest metals.
What’s an alloy?
The properties of pure metals can be changed/improved by mixing them with other metals to make alloys. For example, by mixing copper with tin you can create bronze, which is much harder than pure copper. Steel is iron mixed with small amounts of carbon. Alloy metals are used for a lot of different purposes including alloy wheels for cars.
Can metals be recycled?
The short answer is yes, but different types of metal have various methods and can be recycled more often etc. so it’s best to read up on a metal’s recycling process. Our ASM guide The world of metal recycling will help you.
ASM scrap metal recycling
- Can iron be recycled in the UK?
- What has the most copper in it to scrap?
- How to better understand scrap metal pricing
- Is there a link between copper and brass prices?
- How to make money from cable scrap
- How many different types of copper are there?
- What can I sell to a scrap metal yard?
- Preparing for the collection of scrap metal
- How scrap metal prices have changed in the past decade
- The continued growth of scrap car recycling in the UK
- How To Dispose of Aerosol Cans in the UK
- What to do with radioactive scrap metal
- 5 common metals that can be recycled
- Where to sell scrap metal
- What are different recycled metals used for?