Getting to Know Metal: How the Extraction Process Works

Introduction to metal extraction

Before the metal extraction process begins, you have to know where to find the ores. Naturally occurring rock formations or other solid materials usually contain the necessary metals, metal compounds or valuable minerals.

These ores are processed to extract non-metallic materials (contaminates) from the valuable metals. This material is then refined and processed into metals or metal alloys, a mixture of two or more metals or metals with other compounds.

Metals are hard substances with thermal conductivity, malleability and luster. Most metals have a high melting point, high density, and several are good conductors of electricity.

Other metal characteristics may include corrosion when exposed to seawater or moist air. Iron-based ferrous metals have magnetic properties and high carbon content, making them susceptible to rust and corrosion.

Magnetism is another characteristic of ferrous metals due to the presence of iron. Cobalt, nickel, steel, and several alloys with rare earth metals are magnetic.

Interestingly, iron can lose its magnetic properties and become paramagnetic if heated over 1418°F (also known as the ‘Curie temperature,’ the point where metal loses its magnetic force). Most metals, including aluminum, copper, and gold are not magnetic.

Brazil, China, Russia, Australia and Africa have the most significant metal ore deposits, with iron ore being the most mined metal worldwide.

Iron ore is ~94% of the 3.2 billion tons of metals mined in 2019, and 98% of that iron goes directly into steel production.

Metal extraction process

What is extraction?

It is the process of preparing and separating impurities from mined products to refine the valuable metal within the ore.

There are several different extraction methods depending on the metal and numerous steps within each primary process. Depending upon the hardness of the ore, you may have to repeat some of these steps.

• Screening – The first step is to separate fine particles from the ore to avoid overloading the crusher.
• Crushing – Involves busting the ore rock into smaller sizes to optimize the subsequent grinding process.
• Reclaim – An additional screening process required with most metals.
• Grinding – Also known as pulverization, this step breaks the ore into small pieces to create enough surface area for the separation processes. Large particles are diverted back into the crushing operation as smaller particles move to the separation process.
• Separation – There are four methods of separating impurities, with each one tailored to specific metal ores (based upon their chemical properties):
  • Hydrolytic Method – Crushed ore is placed in a stream of water on a vibrating table to separate impurities from the metal.
  • Froth Flotation – Compressed air is blown into an oil-filled tank to create a froth which allows the impurities to settle at the bottom.
  • Magnetic Separation – This technique separates magnetic metal particles from impurities in the crushed ore with magnetic conveyor belts.
  • Chemical Separation – A solvent is used to dissolve the impurities in crushed ore.

Metal chemistry

Most elements on the periodic table are metals. Metal ore is rarely free of contaminates in its natural state; most are combined in rock and with other elements (ore). The periodic table categorizes metals into several categories:

• Alkali Metals – These metals have chemical reactions with air and water. Often combined with other metals and stored in oil to prevent reactivity. They are in the first column of the periodic table.
  • Lithium (Li)
  • Sodium (Na)
  • Potassium (K)
  • Rubidium (Rb)
  • Cesium (Cs)
  • Francium (Fr)

• Alkaline earth metals – These metals are located in the second column of the chart – salts are reactive with water, while the oxides are basic by nature.
  • Beryllium (Be)
  • Magnesium (Mg)
  • Calcium (Ca)
  • Strontium (Sr)
  • Barium (Ba)
  • Radium (Ra)
• Transition metals – These are the best conductors of electricity, have high melting points and are highly dense. There are forty elements in the middle of the periodic table that fall into this category, ranging from scandium (Sc) to copernicium (Cn).
• Rare earth metals – Rarely occur in nature, highly sought-after and valuable elements. Rare earth metals tend to have high electrical conductivity. Elements that fall into this category range from lanthanum to lutetium, and may also include scandium and yttrium.
• Poor metals – The least reactive of all metals. These elements are located in columns 13-15 of the periodic table, beginning with aluminum (Al).
• Semimetals – Less conductive and more brittle than most metals, these possess properties bordering between metals and non-metals.
  • Boron (B)
  • Silicon (Si)
  • Germanium (Ge)
  • Arsenic (As)
  • Antimony (Sb)
  • Tellurium (Te)
  • Polonium (Po)

Types of ores

There are four basic types of ores based on their identifiable chemical impurities (see chart). These contaminates require removal during the varying metal refinement processes.

• Ores Oxides
• Ores Carbonate
• Ores Sulfide
• Ores Halide

Everyday uses of ore-based metals

Almost all of our everyday items contain metal:

• Automotive and construction use iron, steel and aluminum.
• Jewelry makes use of gold, silver, and platinum.
• Copper is essential to wire making.
• Your cookware and utensils are largely aluminum and steel.
• The galvanizing process uses zinc.
• Food containers, solder and bearings incorporate tin; it’s also the most mined “tech metal,” with almost half going into soldering.
• Thermometers use mercury.
• Cobalt, lithium, molybdenum and vanadium are essential for green energy technologies such as lithium-ion batteries, solar panels and wind turbines.

Future of metal mining

The future of mining is in the sea and stars.

Many countries are proceeding with deep-sea mining (DSM) to search for common metals and rare earth metals. Experts estimate that a section of the Pacific Ocean alone could have more metal and mineral deposits than all land-based mining combined! As scientists and engineers continue to explore whether or not DSM is less destructive than surface mining, its true environmental impact remains unclear.

There are also trace amounts of gold in seawater (one gram/100 million metric tons) ─ however, it is not economically justifiable to filter at this time. The ocean floor contains massive gold deposits, but they are 1-2 miles deep and under a layer of rock. No existing technology is available to justify mining at these depths, but research is ongoing.

As we expand our frontiers, mining asteroids, the Moon and even Mars may be a possibility.

Asteroids vary in composition but are primarily made of iron-nickel – some have high concentrations of rare metals like gold, silver and platinum.

The United States Artemis Program plans to lead a multinational consortium to the moon. The US has already adopted the world’s first space resource laws in preparation for the project. This makes the Moon the most likely target for the first commercial mining operation. We should see the first unmanned flight later this year, with a human-crewed flight to follow in 2024.