Rare earth minerals and resources in the world

doi:10.1016/j.jallcom.2005.04.033

Journal of Alloys and Compounds

Volumes 408–412, 9 February 2006, Pages 1339-1343

https://doi.org/10.1016/j.jallcom.2005.04.033 Get rights and content

Abstract

About 200 rare earth (RE) minerals are distributed in a wide variety of mineral classes, such as halides, carbonates, oxides, phosphates, silicates, etc. Due to the large ionic radii and trivalent oxidation state, RE ions in the minerals have large coordination numbers (c.n.) 6–10 by anions (O, F, OH). Light rare earth elements (LREEs) tend to occupy the larger sites of 8–10 c.n. and concentrate in carbonates and phosphates. On the other hand, heavy rare earth elements (HREEs) and Y occupy 6–8 c.n. sites and are abundant in oxides and a part of phosphates. Only a few mineral species, such as bastnaesite (Ce,La)(CO₃)F, monazite (Ce,La)PO₄, xenotime YPO₄, and RE-bearing clay have been recovered for commercial production. Bayan Obo, China is the biggest RE deposit in the world. One of probable hypotheses for ore geneses is that the deposit might be formed by hydrothermal replacement of carbonate rocks of sedimentary origin. The hydrothermal fluid may be derived from an alkaline–carbonatite intrusive series. Following Bayan Obo, more than 550 carbonatite/alkaline complex rocks constitute the majority of the world RE resources. The distribution is restricted to interior and marginal regions of continents, especially Precambrian cratons and shields, or related to large-scale rift structures. Main concentrated areas of the complexes are East African rift zones, northern Scandinavia-Kola peninsula, eastern Canada and southern Brazil. Representative sedimentary deposits of REE are placer- and conglomerate-types. The major potential countries are Australia, India, Brazil, and Malaysia. Weathered residual deposits have been formed under tropical and sub-tropical climates. Bauxite and laterite nickel deposit are the representative. Ion adsorption clay without radioactive elements is known in southern China. Weathering processes concentrate REE in a particular clay mineral-layer in the weathered crusts whose source were originally REE-rich rocks like granite and carbonatite. The production is increasing in recent years. However, the process of chemical extraction has brought environmental problems.

Introduction

It is said that rare earths are not rare in natural occurrence. It is true for light rare earth elements (LREEs). However, heavy rare earth elements (HREEs) are less common. Furthermore, RE resources are unevenly distributed in the world. The world mine production in 2003 is concentrated in several countries: China, India, CIS, Malaysia, and Sri Lanka [1]. Especially, China occupies more than 90% of the production. The other productive countries are USA, Australia, Canada, South Africa, Brazil, and others. Recent industrial demands for HREE would bring exhaustion of the resources in near future. Exploitation of RE resources also involves environmental problems. One of problems is due to radioactive elements associated with REE in the minerals.

Here, overview of RE minerals and the resources would be useful for the development from now on. In this paper, we first present the mineralogical features of RE minerals. Secondly, the ore deposit types and the world distribution of RE resources are presented with remarks for future developing.

Section snippets

Classification of rare earth minerals and their crystal-chemical features

So far, a total of about 200 distinct species of RE minerals have been described. And crystal structures of about the half have been reported. Miyawaki and Nakai [2], [3] stated that minerals, whose chemical formulae indicate significant contents of rare earths, are defined as RE minerals, even if their contents appear unessential to the minerals. They have reviewed all the reported structures in “Crystal Structures of Rare Earth Minerals”, which is useful for database and a textbook on RE

The ore deposit types of rare earths and the world distribution

The classification of the deposit types is indicated in Table 2 based on Kamitani [5]. The major deposits are classified genetically into igneous, sedimentary, and secondary types. The world distribution corresponding to the classification is shown in Fig. 2.

Bayan Obo, China is the biggest RE deposit in the world. The deposit was formed by hydrothermal replacement of the carbonate rocks of sedimentary origin, but the hydrothermal fluids may be derived from an alkaline–carbonatite intrusive

Bayan Obo deposit, China

Bayan Obo Fe–REE–Nb deposit is located 135 km northwest of Baotou in Inner Mongol Autonomous Province. RE minerals closely associated with the iron ores have been recovered from the iron ore dressing plant. The reported total reserves are at least 1.5 billion metric t of iron (average grade 35%), at least 48 million t of RE oxides (REO) (average grade 6%), and about 1 million t of niobium (average grade 0.13%) [6]. Recent statistics shows 89 million t of REO in China [1]. The principal RE minerals are

Concluding remarks

Recent demands for HREEs are increasing in high-tech industries. Extraction of HREEs from bastnaesite and monazite, even if xenotime causes the excessive production of LREEs and the harmful accumulation of radioactive elements. One way to cope with the situation is to extract HREEs from ion-adsorption clay. This type of clay is produced only in the southern China. It is recommended to the other countries to investigate lateritic clay formed by weathering of granites. Otherwise R&D for mineral

Acknowledgement

This work was partially supported by Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology.

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Rare earth minerals and resources in the world

Abstract

Introduction

Section snippets

Classification of rare earth minerals and their crystal-chemical features

The ore deposit types of rare earths and the world distribution

Bayan Obo deposit, China

Concluding remarks

Acknowledgement

Mineral Commodity Summaries, January 2004

U. S. Geological Survey

Rare Earths

Acta Crystallogr. B

Lithos

Chin. Sci. Chin. (Ser. B)

Demonstration of Geological Features and Genesis of the Bayan Obo Ore Deposit