Driven by the philosophy of low carbon and environmental protection, the new energy sector has become a contemporary driving force in today’s economy. The demand for raw materials in the new energy industry opens a window for the mining industry, generating a new demand for minerals such as lithium, nickel, cobalt, and rare earth. This article will introduce two minerals that are currently attracting significant attention in the field of new energy: lithium and ionic rare earth.
1. Lithium
1.1 Mineral Resources distribution and production
Measured lithium Resources are currently dominated by salt lake lithium and hard rock lithium. The two charts below reflect the main global lithium Resource distribution and the main lithium producing countries as of 2019. At present, lithium Resources and production is centralised in four countries, including Chile and Argentina in South America, Australia, and China. Australia is the largest producer of hard rock lithium, followed by Chile, China, and Argentina, respectively. By 2019, China had 8.78 million tonnes of hard rock lithium Resources and 92.5 million tonnes of lithium brine Resources.
1.2 Lithium deposit classification, grade, mining method, and extraction method
The known lithium deposits include three main categories:
a. Igneous Pegmatites: hard igneous rock, that contain the main ore-bearing minerals spodumene, petalite and lepidolite.
b. Brine: lithium in salt lake, lithium in seawater, lithium-bearing brine in oil and gas fields, and geothermal brine.
c. Sedimentary: mainly divided into clay minerals (structural and adsorption type), and sedimentary hard rock. The main ore-bearing minerals are lithium montmorillonite, illite, borosilicate and zeolite. In addition, jadarite lithium ore in Serbia is also generally classified as clay minerals.
Different types of lithium have different Run Of Mine grades, mining methods, processing, and extraction methods, as shown in the table below.
The development and utilization of different forms of lithium ore differ greatly. The following table lists the key steps from mining to purification of different lithium deposits.
1.3 Cost and Profit
Salt Lake lithium mineral products tend to be more of a downstream final product, while pegmatitic lithium minerals are used as lithium concentrates that require further purification and processing.
The mining cost of salt lake lithium and pegmatite lithium ore is converted to lithium carbonate per tonne equivalent, and the mining cost of salt lake lithium is usually greater than that of pegmatite lithium. However, it should be noted that the final product of salt lake lithium is usually lithium salt (lithium carbonate, lithium chloride) or lithium hydroxide that is close to the end-product, which has a higher value and fewer subsequent purification procedures. The product of pegmatitic lithium after mining and mineral processing is usually lithium-bearing concentrate, which needs more complex mineral processing and extraction technology to produce the final product. Therefore, the overall profit margins of lithium mining and extraction in salt lake is higher than that of pegmatitic lithium. It should be noted that to expand the value chain, some hard rock lithium mining companies in Australia (such as Mineral Resources Limited's Wodgina Lithium Project) are considering the construction of deep processing plants to expand their value chain. However, the large capital expenditure required to build a purification plant also needs to be taken into account.
1.4 Advantages and challenges in the development of various types of lithium deposits
The development and utilisation of pegmatitic lithium ore belongs to the conventional mining field using mature technology, but the equivalent profit margins of comprehensive lithium carbonate are relatively low.
The profit margins of comprehensive lithium carbonate of brine-type salt lake lithium are at an advantage. Investment and cost risks are mainly concentrated in the lithium extraction. Lithium in seawater, geothermal and lithium-bearing brine in oil and gas fields are still in the early study stage.
The mining cost of clay minerals is low, but there are still challenges in the mineral processing and extraction technology. Detailed data for the combined profit margins are not yet available.
2. Rare earth ore
With the rapid development of electric vehicles and wind power generation, there is a growing demand for permanent magnets, driving an increasing demand for rare earth permanent magnet elements. Rare earth elements usually refer to the 15 elements of the lanthanide series with atomic numbers between 57 and 71, and to scandium (Sc) and yttrium (Y), which are geochemically similar to elements of this series. Rare earth is divided into light rare earth and heavy rare earth; the smaller part of the atomic number is a light rare earth, and the larger part is a heavy rare earth. The chart below shows the distribution of rare earth and key minerals in the periodic table released by the United States Department of Energy. Conventionally, the value of heavy rare earth elements is high, but with the development of new energy, the focus of rare earth development is now shifting to rare earth permanent magnet elements.
2.1 Rare earth permanent magnet elements – a hot spot for development
The rare earth permanent magnet elements are mainly samarium, neodymium, and praseodymium, which can be used as raw materials for permanent magnets. Generally, there are two kinds of rare earth permanent magnet materials: samarium cobalt permanent magnet materials and neodymium (NdFeb) permanent magnet materials. Both permanent magnet materials have their own pros and cons, but NdFeb permanent magnet materials are currently used more in permanent magnet motors.
2.2 Ionic Rare earth deposits
Rare earth deposits can be divided into hard rock rare earth deposits and clay rare earth deposits. Ionic rare earth deposits – also known as clay deposits – are more similar to laterite nickel deposits. Ionic rare earth deposits have the following characteristics:
a. Distribution – weathered layers in tropical and subtropical areas.
b. Weathering crust ionic adsorption type (clay minerals) – similar to laterite nickel ore.
c. Parent rock – granite, granodiorite, diorite, etc.
d. The thickness of the ore layers typically range from a few meters to dozens of meters.
e. They have the characteristics of topographic ore control, with gentle hilltops and gentle slopes favourable to the enrichment of rare earth elements.
2.3 Ionic rare earth exploration methods
The means of geological exploration for ionic rare earth deposits can be summarized as follows:
a. Exploration methods:
i. Terrain analysis to determine favourable mineralisation sites.
ii. Geological drilling: Gannan drill, Luoyang shovel, core drilling rig.
iii. On-site rapid titration mineralization detection: handheld XRF.
iv. Geophysical exploration: ground-penetrating radar - control of bedrock.
b. Analytical test methods:
i. Inductively coupled plasma mass spectrometry (ICP- MS).
ii. Chemical analysis method: EDTA titration for ionic rare earth oxides.
iii. Small weight, full moisture testing and testing for hazardous elements such as uranium is also required.
2.4 1.1 General requirements for cut-off grade – China standard
2.5 Mining and mineral processing
The mining technology of ionic rare earth generally consists of pond leaching, heap leaching and in situ leaching. Currently, in situ leaching technology is adopted by most mining projects in China. The main process includes in situ leaching (ammonium sulphate), impurity removal (ammonium bicarbonate), precipitation (ammonium bicarbonate/oxalic acid), and calcination. After calcination, the enriched rare earth oxides are obtained. The rare earth oxides are sold as products to downstream rare earth purification and separation plants.
