Mineral Sands: The Hidden Source of Titanium, Rare Earths and Thorium

Critical minerals & Rare Earth elements
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Beneath seemingly ordinary coastal beaches and dunes lie natural deposits that supply some of the world's most advanced industries. Mineral sands encompass a set of deposits rich in ilmenite, rutile, zircon and monazite, which constitute essential sources of titanium, zirconium, rare earths and thorium.

The growing interest in these formations stems from the nature of the resources they contain. Several of these elements play a central role in modern industrial supply chains, particularly in technologies related to the energy transition, electrification and advanced materials. As global demand evolves, these deposits are increasingly emerging as strategic objects of study and exploitation, at the intersection of geology, industry and resource policy.

This reality gives mineral sands a particular place among natural resources. Their value does not rest on a single material, but on the combination of several minerals with complementary uses, whose importance tends to grow within contemporary economic dynamics.

What are mineral sands?

Mineral sands are natural concentrations of heavy minerals, formed by processes of erosion and sedimentary transport. More specifically, these minerals are originally contained in igneous rocks (such as granite or basalt) or metamorphic rocks (such as schist), which have been fragmented by natural weathering processes and then transported by river systems to form placer deposits in coastal, lacustrine or fluvial environments.

A heavy mineral is defined by a density greater than that of quartz (i.e. more than 2.85 g/cm³), which allows it to be naturally concentrated in coastal deposits through the effect of gravity and wave action. A placer deposit (from the Spanish placer, meaning "sandbank") refers to an accumulation of dense minerals physically concentrated by natural agents such as water or wind, without chemical transformation. [1]

The main components of these sands are rutile (TiO₂), ilmenite (FeTiO₃) and zircon (ZrSiO₄), which account for the bulk of their economic value. In smaller proportions, monazite ([Ce,La,Th]PO₄) is also found, along with other accessory minerals such as xenotime (YPO₄), known for their content of rare earths and thorium [1]. Even when present in limited quantities, these minerals contribute to the interest of mineral sands due to the specific uses of the elements they contain.

Table 1: The main minerals in heavy sands

Mineral Chemical formula Primary resource Industrial use
Ilmenite FeTiO₃ Titanium (TiO₂ pigment) Paints, plastics, coatings
Rutile TiO₂ Titanium (pure metal) Aerospace, medical industry, electrodes
Zircon ZrSiO₄ Zirconium Ceramics, refractories, nuclear
Monazite (Ce,La,Th)PO₄ Rare earths + Thorium Magnets, catalysts, nuclear energy

Deposit formation and global distribution

How are these deposits formed?

The formation of mineral sands results from a succession of geological processes spanning millions of years. Originally, the minerals are contained in igneous and metamorphic rocks. Through the combined effects of chemical weathering and mechanical erosion, these rocks gradually fragment and release mineral grains of various sizes. These particles are then carried by natural agents such as rivers, waves and wind, which transport them sometimes over long distances.

During this transport, sediments are progressively sorted according to their physical properties, particularly their density and grain size. Lighter minerals, such as quartz, are more easily dispersed, while denser minerals tend to accumulate in certain areas. This natural sorting process, repeated over time, leads to the progressive concentration of heavy minerals in specific environments, notably beaches, coastal dunes or certain river systems.

These accumulations correspond to placer deposits, meaning natural concentrations of dense minerals formed by physical processes, without chemical transformation [1]. The example of certain regions of West Africa illustrates this mechanism well: metamorphic and cratonic rocks are weathered upstream on the continent, their liberated minerals are then carried by river systems to the coast, where the action of coastal currents and aeolian processes favours their progressive concentration in coastal sands, as demonstrated by the Grande Côte deposit in Senegal. [6]

Leucoxene corresponds to an altered form of ilmenite, generally enriched in titanium dioxide. This natural transformation modifies its composition and can increase its economic value in titanium production chains.

Where are the main deposits found?

Mineral sand deposits are distributed across the globe, but certain regions stand out for the size and richness of their reserves. Australia and Africa are the main producers, particularly for titanium-bearing minerals and zircon. [1] In Australia, deposits are present in all states and in the Northern Territory, associated with modern and ancient beaches and dunes, from Cape York (Queensland) to central New South Wales, as well as in Western Australia.

Ilmenite, rutile and zircon: the titanium minerals

Titanium is one of the most sought-after metals for the industrial and energy transition. Yet its global production relies almost exclusively on two constituents of heavy sands: ilmenite and rutile. This section presents their properties, their applications, and their role in modern industries.

Ilmenite: the world's primary source of titanium dioxide

Ilmenite is an iron and titanium oxide (FeTiO₃) that also contains traces of magnesium, manganese and vanadium. Exploitable deposits generally exhibit high titanium dioxide content, often exceeding 45%, which enables their economic recovery [4]. It constitutes the main raw material used to produce this compound, which is widely used in the manufacture of paints, plastics and various industrial coatings.

More broadly, titanium-bearing minerals — notably rutile, ilmenite and leucoxene — are primarily used to produce titanium dioxide in pigment form, which remains the most widely used white pigment in industry. [1]

Rutile: a pure form for high-precision applications

Rutile is a natural form of titanium dioxide (TiO₂), red to black in colour, whose theoretical TiO₂ content reaches 100%, although impurities (Fe₂O₃, Cr₂O₂) generally bring it down to between 93 and 95% in natural deposits. [5] This high purity makes it the mineral of choice for producing titanium metal destined for the aerospace, medical and defence sectors, as well as for manufacturing welding electrodes. [1]

Titanium is also among the critical minerals recognised as essential to modern technologies, particularly renewable energy, batteries, electronics and electric vehicles. It is also listed by the UN Expert Group on Energy Transition Minerals. [7]

Monazite: a bridge between rare earths and thorium

Among the constituents of heavy sands, monazite occupies a unique place. Often present in small proportions within deposits, this mineral is simultaneously a source of light rare earths and thorium, two resources at the heart of the energy transition and next-generation nuclear energy. This makes it a direct link between sedimentary geology and industrial strategy.

Composition and properties of monazite

Monazite is a rare earth phosphate containing primarily cerium and lanthanum, as well as a variable proportion of thorium, generally between 5 and 12% (typically around 7%). [1] It occurs as small, brown, resinous and relatively dense crystals, found in granitic and gneissic rocks as well as in their sedimentary residues, known as monazite sands. It also represents a major commercial source of thorium. [3]

In Western Australia, certain mineral sand deposits can contain up to 10% heavy minerals, of which 1 to 3% is monazite. The latter typically contains between 5 and 7% radioactive thorium, as well as 0.1 to 0.3% uranium. [1]

Monazite as a source of rare earths

Light rare earths constitute a subgroup of the 17 rare earth elements. These elements are used in the manufacture of permanent magnets, industrial catalysts and advanced electronic components — applications directly linked to the energy transition.

Nearly all 17 rare earth elements can be extracted from mineral sands. [2] In particular, monazite is recognised as the world's primary commercial source of cerium. [3] The rare earths extracted from this phosphate play a structural role in the energy transition: the permanent magnets used in wind turbines and electric vehicle motors depend notably on neodymium and lanthanum, two elements naturally contained in monazite.

Conclusion

Within a single type of sedimentary deposit, mineral sands concentrate at least three major strategic resources for the energy transition: titanium, extracted from ilmenite and rutile; light rare earths, derived from monazite; and thorium, co-present in that same phosphate.

As global demand for titanium, rare earths and thorium intensifies — driven by low-carbon technologies, electric vehicles and the next generation of nuclear reactors — these deposits are increasingly emerging as geological vectors of high strategic value. This explains the growing interest from players in the mining and energy sectors in better understanding and responsibly exploring these resources.

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References


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