The Elements of Minerals

To understand why some minerals are “critical”, you first need to understand what a mineral is. Minerals are made of elements. Elements are the chemical building blocks of minerals. There are 118 known elements. Every mineral is made from one or more of these elements. Some elements, such as oxygen and silicon, are very common (Figure 1). Most elements are much rarer. Have you ever heard of the element neodymium? Even if you have not, you probably use it every day. Neodymium is an important part of smartphones (Figure 2) and other electronic devices such as headphones.

Minerals are made of elements connected to each other in a pattern. Each mineral has specific elements in a specific pattern. Think of the elements as building blocks with different colors. You can arrange the blocks in an organized pattern, or rearrange the same blocks to make a completely different pattern. Or you can use different colors of blocks in different patterns. There are many possibilities. It is the same for minerals. Each type of mineral has a unique combination of elements and the way they are arranged.

For example, diamond and graphite are made of the exact same element: carbon. But they are totally different minerals because the carbon atoms are arranged in different ways. In diamond, carbon atoms are packed very tightly together to create the hardest mineral on Earth [1]. In graphite, carbon atoms are in layers that you can break apart just by pressing on them, making it one of the softest minerals [2]. Graphite is in pencils. You break the connections between layers of carbon atoms when you write with a pencil. Other minerals are distinct in both composition and the pattern of their elements.

Why are All Minerals Not Found Everywhere?

Every mineral has a particular set of conditions at which it forms. These are depth (how deep in the Earth), temperature (how hot), and environment (what elements are present or if water or magma are around). For example, diamonds form deep underground at very high pressures. Graphite forms in shallower parts of the Earth under lower pressures. Deep carbon creates hard, dense diamond, while shallow carbon creates soft, weak graphite.

The ingredients (carbon) and conditions for diamonds have occurred in some places but not others. Look for the diamond symbol on the map of the world (Figure 3) to see which places have a lot of diamonds and which do not. Only a few places in the world have diamonds! Graphite is a more common mineral than diamond. However, there are only a few places in the world where it occurs in abundance in a single place, where it can be mined.

Here is another example: copper conducts electricity well, so many wires are made of copper. If you have a smartphone, the most abundant metal in it is probably copper (Figure 2). There is a long belt of copper deposits along the west coast of North and South America (Figure 3). The processes that form a major type of copper deposit occurred there. Other parts of the world have scattered deposits of copper. If a particular mineral-forming process is rare, the mineral may only occur in a few places in the world. Cobalt is a rare mineral that most countries want. Only a few have good deposits of it.

So, why are all minerals not found everywhere? Not every place has the same elements and the same geological history. To find a particular mineral, geologists use knowledge of its composition, element arrangement, and the conditions needed to form it.

What Makes a Mineral “Critical”?

Imagine that you are in charge of a country. You want everyone in your country to have enough food, medical care, transportation, and technology such as phones and computers. All of these require minerals. What do you do if your country has enough of some of the minerals you need but not others? A mineral is “critical” if it is needed to make important things but a country does not have a good supply of it. The definition of critical minerals is not a scientific one. It is based on how people need and use minerals. Different countries have different lists of minerals that are “critical” for them.

Here is something important to know: lists of “critical minerals” include minerals and elements. In fact, most are elements and only a few are minerals. Why are more elements listed than minerals? One reason is that most elements occur in more than one type of mineral. For example, the element lithium [3] is an important ingredient of rechargeable batteries. Lithium batteries are in computers, phones (Figure 2), and electric vehicles. Lithium occurs in different minerals. It also occurs in salty water in some desert lakes. The specific lithium-containing substances are not “critical”, just the lithium. So, we list the element that we want and need (lithium) and not seven or more different minerals that contain lithium.

Some critical minerals are minerals: the mineral graphite is “critical” rather than its element, carbon. Why? Because the specific atomic arrangement of carbon in graphite makes it useful for batteries and many other things. Diamond also consists of carbon, but diamond’s arrangement of carbon changes the properties of the mineral. The properties of graphite make it useful in rechargeable batteries. So, graphite is listed because that is the form of carbon that is needed. Does it surprise you that graphite is a critical mineral and diamond is not?

Another example is the mineral fluorite (also known as fluorspar). The “fluor” part of the name is from the element fluorine, which has many uses. Fluorite is listed as a critical mineral because it is by far the most important source of fluorine. It would be most correct to say “critical minerals and elements”, but this is typically shortened to “critical minerals”.

Which Minerals are Critical Now?

The United States [4], Canada, and the European Union have similar lists of critical minerals. There are some differences because the geology of each region is different. This means that some countries have enough of some minerals but other countries with different geology do not have enough of these minerals or do not have a good way to get them. Most countries’ lists have about 50 critical minerals (and elements). Here are some “superstars” that appear on every list:

Lithium

Lithium forms in salty desert lakes and in some minerals that form in rocks, such as granite. Lithium is special because it stores energy in rechargeable batteries. It is used in phones, computers, electric vehicles, and some medicines. Fun fact: lithium is lighter than water!

Copper

Copper forms near some types of volcanoes. It is special because it conducts electricity and is soft enough to make thin wires. Copper is used in electrical wires, wind turbines, motors, and circuits. Fun fact: when copper reacts with the atmosphere, it turns green!

Cobalt

Cobalt forms where hot fluids dissolve metals from rocks in continents. It is special because it makes lithium batteries more stable and longer lasting. Cobalt is used in phones, computers, and electric vehicles. Fun fact: cobalt was named by German miners who thought the element was a “goblin” that harmed other metals such as silver.

Rare Earth Elements

Rare earth elements are a group of 17 related elements. They form in many different environments but mostly in very small amounts. Rare earth elements are special because they make super-strong magnets and help make phone displays colorful. They are used in computers, phones, headphones, and microphones. Fun fact: every time you look at a phone or flatscreen TV, you are staring at rare earth elements!

A country’s list of critical minerals may change with time. Perhaps a country will find a new, reliable source of the minerals it needs. This could happen if a country opens a new mine or makes a secure agreement with another country that has the critical minerals. An exciting reason for change is if new discoveries remove the need for mining some minerals that are currently considered critical. For example, perhaps it will be possible to recycle batteries more efficiently. Or maybe a new type of material will be invented using elements other than the ones we rely on now. Scientists and engineers are always working on finding new materials and uses that work better than the ones we have now. Maybe someday you will too!

Why Should We Care About Critical Minerals?

We all use many different minerals in our daily lives. Without minerals, we would not have smartphones or computers. We would not be able to use energy from the sun or wind. Human health depends on minerals used to grow food and create medicines. Countries that do not have enough of the critical minerals they need must get them from other countries, meaning countries depend on each other for critical minerals. Your smartphone might contain lithium from Australia, cobalt from central Africa, copper from Chile, and rare earth elements from China. So, as you can see, critical minerals connect the world!

Glossary

Mineral: ↑ A solid material made of elements in an organized (not random) pattern. Each mineral is defined by the elements it contains and the arrangement (pattern) of the elements.

Element: ↑ A chemical substance made up of only one type of atom.

Geological History: ↑ The sequence of events and processes that have created and shaped the Earth over time, such as formation of minerals, development of landscapes, and changes in environmental conditions.

Critical Mineral: ↑ A mineral that a country decides is essential for its economy and security but that it does not have enough of, so it must rely on other countries to supply the mineral.

Rare Earth Elements (REE): ↑ A group of 17 elements that are key components of modern technologies such as magnets and batteries. They are not actually rare, but they rarely occur in high concentrations.

Conflict of Interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

Partial funding for Donna Whitney’s and Bob Bodnar’s research on minerals was provided by grants from the US National Science Foundation, including grant # EAR-2342604 to Whitney.

AI Tool Statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.