Critical minerals (Part 4): Rare earth elements – strategic resources at the intersection of geology, technology, and global responsibility
Michael Mackiewicz (USA)
In earlier articles of this series, lithium and cobalt from the list of the Top 10 critical minerals – lithium, cobalt, nickel, graphite, manganese, rare earth elements, tungsten, vanadium, bismuth and antimony – were discussed relative to their value to mineral collectors,advanced technologies and the global economy. Rare earth elements (REEs), sometimes referred to as rare earth materials, are veryinteresting in this respect and will be explored next.
REEs are a group of 17 metals that include the 15 lanthanides – elements with atomic numbers 57 through 71 on the periodic table, plus scandium (Sc) and yttrium (Y).
Lanthanides are a group of 15 metallic elements in the periodic table, ranging from lanthanum to lutetium (atomic numbers 57–71). They exhibit similar chemical characteristics, and are often called “rare earths” not because they are scarce, but because they are hard to extract from ore. These elements are highly reactive and known for their magnetic and light-emitting properties, which make them valuable in electronics, magnets, and display technologies.
Lanthanides are found together in many minerals and have very similar sizes and properties. Even though scandium and yttrium are not part of the lanthanide series on the periodic table, they are grouped with them because they display nearly the same chemical behaviour and often occur in the same types of rocks. The main difference is that scandium and yttrium are lighter and have slightly different atomic structures, but they still act like lanthanides when forming minerals and chemical compounds.
Despite the factthatthey are called “rare”, many REEs are more common in the Earth’s crust than metals like copper or lead andthis specific designation refers to how rarely they are found in rich, readily mined concentrations. REEs are important for modern technology because of their special magnetic, optical and chemical properties.
Where do REEs come from? Rock types containing REE-bearing minerals
Rare Earth Elements (REEs) do not occur as pure metals in nature. Instead, they are found in minerals where they are bonded with other elements like phosphorus, fluorine, or oxygen. Although REEs are classified as metals because they can conduct electricity, have a lustrous surface, and can be shaped without breaking, they almost never appear in metallic form naturally. Common REE-bearing minerals include bastnäsite, monazite, xenotime and loparite, which must be processed to extract the elements. Understanding these minerals is important, as is knowing the types of rocks and geological processes.
[TABLE 1]
| Rock type | Countries | Primary REE-minerals | Deposit type |
|---|---|---|---|
| Carbonatite | China, Canada, Brazil, Russia | Bastnäsite, Monazite | Magmatic |
| Peralkaline igneous rocks | Greenland, Canada, Russia | Eudialyte, Loparite | Magmatic |
| Monazite-bearing placer deposits | India, Brazil, Australia | Monazite | Placer |
| Ion-adsorption clays | China, Myanmar | Adsorbed REE ions | Weathered clay |
| Phosphorite | Morocco, United States | Monazite, Xenotime | Sedimentary |
| Granite | China, Russia | Monazite | Magmatic |
| Bastnäsite-bearing veins | United States, China | Bastnäsite | Hydrothermal |
| Xenotime-bearing sandstones | Malaysia, Brazil | Xenotime | Sedimentary |
Table 1 shows different kinds of rocks that contain REEs and the countries where these deposits occur. It also lists the main minerals and the rock type, which explains how the REEs became concentrated. For example, carbonatite rocks in China and Brazil often contain bastnäsite and monazite, while ion-adsorption clays in China and Myanmar hold REEs in weathered clay, highlighting the global distribution and diversity of REE sources.
Deposit type refers to the geological process that forms the deposit. Magmatic deposits form when magma cools and crystallises, concentrating REEs in minerals like bastnäsite and monazite. Placer deposits develop when weathering and erosion move heavy minerals such as monazite into river or beach sands. Weathered clay deposits occur when REEs stick to clay minerals during intense tropical weathering of granitic rocks.
Sedimentary deposits form in layered sediments, often linked to phosphorites or sandstones, while hydrothermal deposits occur when hot, mineral-rich fluids precipitate REEs in veins. Together, these processes explain why REEs are found in many different environments and why understanding both rock type and deposit type is essential for locating and mining these valuable resources.
Distribution of rare earth elements in rocks and minerals
Understanding how rare earth elements (REEs) are distributed among different rock types and minerals is essential for mining industries in evaluating potential sources and in making business decisions as to whether or not to mine and extract REEs.
| Light REEs (LREE) | Heavy REEs (HREE) |
|---|---|
| Lanthanum (La) | Terbium (Tb) |
| Cerium (Ce) | Dysprosium (Dy) |
| Praseodymium (Pr) | Holmium (Ho) |
| Neodymium (Nd) | Erbium (Er) |
| Promethium (Pm) Synthetic, radioactive | Thulium (Tm) |
| Samarium (Sm) | Ytterbium (Yb) |
| Europium (Eu) | Lutetium (Lu) |
| Gadolinium (Gd) | Scandium (Sc) |
| Yttrium (Y) |
Due to size differences, REEs can fit into the crystal structures of a wide range of rock-forming minerals, particularly phosphates and carbonates, during crystallisation. Some minerals prefer light rare earth elements (LREEs), while others favour heavy rare earth elements (HREEs), depending on their chemical composition and the conditions under which they formed. Table 2also lists which REEs are identified as LREEs and HREEs.
Fig. 1 summarises the occurrence of LREEs and HREEs across major rock types, including carbonatites, granites and pegmatites, illustrating their distribution within common lithologies. Carbonatites and granites contain the most REEs overall, with carbonatites being especially rich in LREEs. Alkaline igneous rocks and pegmatites also contain several REEs, showing a mix of both LREEs and HREEs.
Rocks that contain xenotime or thorvittite tend to have more HREEs than LREEs. Synthetic materials and laterites show fewer REEs but still contribute to the overall distribution. These patterns reflect not only geochemical preferences but also the specific minerals that host REEs within each rock type.
Information presented in Fig. 2 highlights the typical REE concentrations found in individual minerals, expressed as a percentage by weight. Each horizontal bar represents a mineral, arranged from lowest to highest REE content and colour-coded to indicate whether it is rich in LREEs, HREEs or contains a mix of both. Bastnäsite, xenotime and monazite exhibit the highest concentrations, making them prime targets for mining and extraction. Bastnäsite and monazite are predominantly LREE-rich, while xenotime and zircon favour HREEs.
Minerals such as allanite and loparite contain both subgroups, and despite their low REE concentration, ion-adsorption clays are valued by industry because their HREE content is more accessible. Together, Figs. 1 and 2 provide complementary insights into REE distribution across rock types and minerals, which are necessary for evaluating potential REE resources for mining, processing and extraction.
Although over 200 minerals are known to contain REEs in trace or measurable amounts, only a handful are rich enough to be considered potential sources for mining. Most are too rare, too low in REE content, or too complex to process. For mineral collectors, mineralogists and mining geologists, understanding these patterns helps in identifying REE-bearing specimens and evaluating their scientific or economic significance.
Collector-prized REE minerals
REE minerals are appreciated and valued by both collectors and mineralogists for their colour, form and rarity, not just their chemical composition. The vivid fluorescence of xenotime and the intricate crystal habits of bastnäsite make them sought-after additions to any mineral cabinet. The five minerals listed below are especially prized for their aesthetic appeal and mineralogical interest.
- Bastnäsite (Fig. 3): A yellowish-brown to honey-brown to reddish mineral with a vitreous lustre and pyramidal crystal habit, from Zagi Mountain in the North-West Frontier Province of Pakistan. It is one of the few REE minerals with significant industrial and collector interest.
- Monazite (Fig. 4): A reddish-brown to yellow mineral forming in prismatic or granular habits. From the Ilímaussaq complex in Greenland. Its colour and radioactivity make it a distinctive specimen among collectors.
- Xenotime (Fig. 5): A yellowish to brown mineral with tetragonal crystals and strong fluorescence under UV light. The mineral may also contain minor HREEs, Ca, U, Th, Si and F. It is found in pegmatites from Hidra in Norway.
- Hydroxylbastnäsite (Fig. 6): Occurs as platy tabular hexagonal crystals in brown to pale apricot to marmalade orange hues, typically embedded in dolomite-lined vugs from Luzenac in France.
- Euxenite (Fig. 7): A black to brown mineral with a submetallic lustre and complex crystal structure. Found in feldspar quarries in granite pegmatite dykes from Håverstad, Iveland, Agder, in Norway. Its composition includes multiple REEs and makes it a favourite among mineralogists.
Industry-focused REE minerals and their economic importance
While mineral enthusiasts admire REE minerals for their colour and form, industry values them for their REE content and extractability. The most economically important REE minerals, bastnäsite, monazite, xenotime and loparite, are used in permanent magnets, phosphors, catalysts and alloys.
The amount, quality and how easily a rock can be mined and processed help determine how much REE content it offers. This helps assess whether the rock is valuable enough to mine. Fig. 2 reveals how much rare earth element (REE) content is typically found in different minerals. Bastnäsite, monazite and xenotime have the highest REE percentages, often above 60%, making them important sources for extraction. Minerals like eudialyte, apatite and ion-adsorption clays contain much lower REE levels, which means that more material must be processed to obtain the same amount of rare earths.
| REE-bearing mineral | REE content by weight | Rock type mineral found in | Ease of extraction scale: 0-10, (0 = easy) |
|---|---|---|---|
| Bastnäsite | 65–75% | Carbonatites and associated igneous rocks | 4 |
| Monazite | 55–65% | Heavy mineral sands, placer deposits | 3 |
| Xenotime | Up to 61.4% | Placer deposits and pegmatites | 3 |
| Ion-adsorption clays | 0.05–0.5% | Weathered bedrock (lateritic deposits) | 2 |
| Pyrochlore | Up to 16% | Carbonatites and associated igneous rocks | 3 |
| Eudialyte | ≈2.3% | Syenites and other igneous rocks | 2 |
| Allanite | 14–33% | Granites, syenites, metamorphic rocks, skarns | 3 |
| Apatite | 0.04–6% | Apatite-rich iron ores, carbonatites, igneous rocks | 2 |
| Zircon | ≈3.78% | Igneous and metamorphic rocks | 2 |
| Loparite | Up to 30% | Carbonatites | 3 |
Table 3 provides additional information on which rock type each mineral is typically found in and how easy it is to extract the REEs. Most REE-bearing minerals score low on the ease-of-extraction scale, with none rated above 4 out of 10 (a rating of 10 indicates ease of extraction). This information highlights the technical challenges and environmental concerns involved in separating REEs from complex mineral structures.
Even minerals with high REE content, like bastnäsite and monazite, require specialised processing, increasing costs. Together, Table 3 and Fig. 2 show that both REE concentration and extraction difficulty must be considered when evaluating mineral resources.
The hidden challenges of mining specifically for REEs
REEs are never found as pure metals in nature; instead, they occur in minerals mixed with other elements such as phosphorus, fluorine and oxygen. Because of this, REEs are typically recovered through complex chemical processing of mineral concentrates. An ore is a naturally occurring rock or mineral deposit that contains enough valuable material, such as REEs, thorium or uranium, to make mining worthwhile. For an ore to be economically viable, the profit from extracting the REEs must exceed the cost of mining and processing.
Some of the most challenging sources of REEs include carbonatite-hosted deposits and ion-adsorption clays, both of which require specialised refining. Deep-sea REE-rich muds and polymetallic nodules, as well as peralkaline igneous deposits, also contain REEs but are difficult to process due to technical, environmental and economic constraints. These factors make REE extraction energy-intensive and costly, even though the elements are essential for modern technologies.
REEs are critical for high-performance applications. As demand grows for electric vehicles, renewable energy systems, and digital infrastructure, the need for REEs continues to rise. However, REEs’ strong bonding in mineral lattices, their frequent co-occurrence with radioactive elements, and the physical and chemical properties of the host minerals, such as fine grain size, low solubility, and complex mineralogy, make their extraction technically difficult and economically challenging. In short, REEs are indispensable for innovation, but their recovery remains one of the most complex tasks in mineral processing.
Even when REEs are present, they are often in low concentrations and dispersed across large volumes of rock, which makes mining costly. In other cases, such as when REE-bearing minerals also contain thorium or uranium, radioactive waste is generated as a by-product, rendering safe disposal costly. There are also significant REE resources on the ocean floor, and countries actively exploring or researching deep-sea REE recovery include China, Japan, South Korea, India, Russia, the US, Germany and Brazil. However, deep-sea mining remains risky, expensive and controversial, and is not yet practical at scale.
Beyond the science and economics, there are serious ethical and environmental concerns. Mining can disrupt ecosystems, contaminate water sources, and generate hazardous waste. In some regions, REE mining has led to deforestation, soil degradation, and health risks for local communities. Therefore, companies are under increasing pressure to demonstrate that their REEs are responsibly and ethically sourced. One promising solution being explored by researchers is to recycle REEs from electronic waste and develop alternative technologies that reduce or eliminate the need for REEs altogether.
Global mining and processing of REE deposits
Rare earth elements (REEs) are essential to modern technology, especially in permanent magnets, phosphors, catalysts and high-strength alloys. However, over 60% of the world’s REE production currently comes from China, raising concerns about supply chain security, geopolitical dependence, and ethical sourcing.
Fig. 8 shows where REEs are mined, processed or both, in countries around the world. Countries such as China, Australia and the US are already active in mining or processing. Some countries, such as Brazil, India and Vietnam, are marked in lighter blue on the map to indicate they may become important in the future for REE production. The map helps visualise which regions are leading now, and which ones could grow in REE supply.
REE recycling is still in its early stages compared to cobalt, but progress is accelerating. Europe and Japan are leading efforts to recover REEs from discarded electronics, magnets and fluorescent lamps. China has begun scaling up recycling from industrial waste and end-of-life products. The US is investing in pilot programmes and research initiatives to develop domestic REE recycling capacity. India is exploring partnerships and incentives to support REE recovery from electronic waste.
Environmental and ethical dimensions
Mining REEs also comes with significant trade-offs. In China, where most REEs are produced, mining often occurs in regions with limited environmental oversight. Open-pit mining and chemical leaching used in ion-adsorption clay deposits can lead to deforestation, soil degradation and contamination of water sources with radioactive and acidic waste.
The human dimension is equally critical. In some regions, REE mining has displaced communities, degraded agricultural land, and exposed workers to hazardous conditions. Informal mining operations, especially in Southeast Asia and parts of Africa, raise concerns about labour rights, health risks and community neglect. These societal issues are directly connected to ‘critical minerals’ and become more urgent as global demand for REEs grows.
New technologies are being developed, such as REE-free magnet designs and more effective recycling methods that aim to reduce reliance on mined REEs. These innovations include ferrite-based magnets, nanocomposite materials, and solid-state devices that minimise or eliminate REE use. Improved recycling systems are also being developed to recover REEs from discarded electronics, magnets, and lighting components.
A mineral group for the moment
REEs were once used mainly in glass polishing and colourants. However, today, they are central to the global economy: powering electric vehicles, wind turbines, smartphones, and defence systems. And minerals that contain rare earth elements (REEs) are admired by collectors for their vivid colours and unique crystal shapes, but they are also important to modern technology. These minerals affect global trade and are tied to international politics, influencing how countries cooperate or compete in the tech industry.
Whether appreciated for their mineralogical beauty or extracted for their technological utility, REE minerals connect geology to global economic, environmental and social challenges, prompting important questions:
- Where do REEs come from?
- How are they being mined and processed?
- And how can we manage their use in ways that are ethical, sustainable and scientifically informed?
Summary
REEs are a mineral group at a critical junction. One roadleads to mineral showcases filled with bastnäsite’s honey-coloured crystals and xenotime’s fluorescent glow, while the other powers the technologies of tomorrow. In their natural form, REEs can be visually captivating, but they are also tied to pressing global issues: environmental degradation, ethical sourcing, and supply chain vulnerabilities.
As the demand for critical minerals grows, society must think carefully about how we use the Earth’s resources. It’s not just about what looks beautiful, what industries need to meet demands placed on them, or what global economics rely on – it is about how we balance innovation with responsibility, and how we ensure that the minerals powering our future are sourced and managed with care.
References
- U.S. Geological Survey. (2025). Rare Earths Statistics and Information. National Minerals Information Center. Retrieved from USGS Rare Earths
- Rezaei, M., Sanchez-Lecuona, G., & Abdolazimi, O. (2025). A Cross-Disciplinary Review of Rare Earth Elements: Deposit Types, Mineralogy, Machine Learning, Environmental Impact, and Recycling. Minerals, 15(7), 720. https://doi.org/10.3390/min15070720
- Chen, P., Ilton, E. S., Wang, Z., Rosso, K. M., & Zhang, X. (2025). Global rare earth element resources: A concise review. OSTI.GOV. Retrieved from OSTI Rare Earth Review
- RRUFF Project. (n.d.). RRUFF Database of Raman spectra, X-ray diffraction and chemistry of minerals. Retrieved November 7, 2025, from https://rruff.info
- Mindat.org. (n.d.). Mineral information and data. Retrieved November 7, 2025, from https://www.mindat.org