Process Mineralogy Characteristics of Lijiagou Pegmatite Spodumene Deposit, Sichuan, China

Abstract

Ljiagou pegmatite spodumene deposit is part of the Ke’eryin ore-field in the central Songpan-Garze Fold Belt of Sichuan, China. After recent exploration and assessment, it has been established as a new super-large spodumene deposit. In order to determine the processing characteristics of the ore and assess its industrial value, based on detailed microscopic and hand specimen observations, this study employs various methods and techniques, including X-ray powder diffraction (XRD), electron probe microanalysis (EPMA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), chemical element analysis, chemical phase analysis and the mineral liberation analyzer system (MLA). The average grade of lithium ore is 0.86%, making it a low-grade ore with 84.1% of Li derived from spodumene. The Li grade decreases with increasing depth, and the samples from shallower depths are easier to dissociate. The spodumene exhibits a wide range of grain sizes and is highly heterogeneous, requiring multiple stages of grinding. Based on the liberation characteristics, it is recommended to grind the material to −0.075 mm before entering the final flotation process.

1. Introduction

Lithium (Li), with atomic number 3 and the highest negative electrode potential of all elements, is the most chemically active metal element. The elementary form of lithium is silvery white, and it is the lightest metal. Due to its distinct physical and chemical properties, lithium holds significant value and finds wide-ranging applications in various industries, including batteries, ceramics, glasses, greases, medicines, and chemicals. Its significance extends to the economy and the defense industry. Moreover, lithium’s importance is globally recognized, as evidenced by its inclusion as one of the 14 key raw materials by the European Union, its classification among the 43 important mineral resources in the United States, and its designation as one of China’s 24 national strategic mineral resources.

Owing to continuing exploration, identified lithium resources have increased substantially worldwide and total about 89 million tons as of 2021. Among them, Bolivia ranks first with 21 million tons, followed by Argentina with 19 million tons, Chile with 9.8 million tons, Australia with 7.3 million tons, and China ranking fifth with 5.1 million tons [1]. Although the lithium markets exhibit regional variations, the global distribution of end-use markets is estimated as follows: batteries account for 74%, ceramics and glass for 14%, lubricating greases for 3%, continuous casting mold flux powders for 2%, polymer production for 2%, air treatment for 1%, and other applications for 4% [1]. With the development of electric vehicles and energy storage technology, the usage of global lithium resources has changed significantly. The global market for lithium batteries has increased by nearly 132% from 2013 to 2018, making this the predominant industrial use for lithium. Sales of new electric vehicles have increased by a factor of 10 from 2012 to 2018. According to the planned development of electric vehicles by major global automobile manufacturers and governments, the annual growth rate will be >35% from 2018 to 2025, and the proportion of lithium used for this purpose will be >80% by 2025 [2]. Major lithium producers in China mostly have medium to long-term expansion plans [3]. With most of the projects currently under construction, it will be difficult to achieve a high-volume release of lithium resources prior to 2025, resulting in a tight supply in the medium to long term.

Granitic pegmatite-type lithium deposits are the most important types of hard rock-type lithium deposits, which are dominant in China [4,5]. For hard rock lithium deposits, determining the processing characteristics of the ore and lithium-bearing minerals is an essential step in the development of a lithium resources. The content of Li in the Earth’s crust is approximately 0.0065%, and there are over 150 known lithium-bearing minerals, including spodumene (2.91%–7.66% Li₂O), amblygonite (10% Li₂O), petalite (3.5%–4.9% Li₂O), lepidolite (1.23%–5.9% Li₂O), zinnwaldite (3.4% Li₂O), hectorite (1.2% Li₂O), and jadarite (7.3% Li₂O). In addition to lithium, ores typically contain a high content of Rb, Cs, Be, Ta, Nb, and Sn which are associated elements that can be recovered as by-products. Common separation processes for lithium ore involve manual separation, flotation, thermal cracking, heavy medium beneficiation, magnetic separation, and a combination of these in industrial use, depending on the type, composition, and properties of the ore [6,7,8,9,10,11,12].

The rare metal resources are abundant in western Sichuan Province. In the past 9 years, many discovered lithium deposits with significantly expanded resource reserves are distributed in this area, and Lijiagou deposit is one of them, which is located in the renowned Ke’eryin rare metal ore field [13]. Through recent exploration work, this deposit has been established as a super-large spodumene rare metal deposit, and there is an urgent need for an accurate assessment of the economic value of the ore. This study aims to reveal the distribution and enrichment patterns of lithium in the ore. By conducting systematic mineral processing research, the objective is to understand the ore’s processing characteristics, gradually reduce the head grade of the ore, and improve the utilization and recovery rates of lithium through subsequent beneficiation tests. These efforts aim to identify the reasons for the low grade and challenging beneficiation of spodumene ore and to promote the engineering and industrial development of the comprehensive utilization of rare element resources in the region.

2. Geological Background

Ljiagou spodumene deposit in Jinchuan, Sichuan, China is located in the southeast part of the Ke’eryin rare metal ore field in western Sichuan. It is in the middle of the Songpan-Garze orogenic zone, and the strata exposed in the area are mainly the Middle Triassic Xikang Formation and Zagunao Formation (T₂z), the Late Triassic Zhuwo Formation (T₃zh), and the Late Triassic Xinduqiao Formation (T₃x). Lithologies include grey-black felsic sandstone, siltstone, sericite slate, argillaceous slate, and limestone. Structures in the area are associated with the compound Ke’eryin anticline and northeast-oriented faults. Granitic pegmatite veins occur in clusters at distances of 0–5000 m from the Ke’eryin rock mass, and these veins show horizontal and vertical compositional zoning, In the horizontal direction, outwards from the granitic body, the following are successively exposed: (I) a microcline pegmatite zone (0–800 m from the Ke’eryin rock mass), (II) a microcline albite pegmatite zone (800–1500 m), (III) an albite pegmatite zone (1500–2300 m), (IV) an albite spodumene pegmatite zone (2300–5000 m), and (V) lepidolite pegmatite veins and quartz veins (>5000 m) (Figure 1b).

Exposed strata within the mining area (Figure 1c) are of the Upper Triassic–Jurassic Zhuwo Formation (T₃zh) and Quaternary strata (Q). The Zhuwo Formation is widespread in the area, and hornfels has formed from sedimentary rocks of the littoral–neritic facies, characterized by rhythmic interbeds of carbonaceous pelite, calcareous quartz–feldspar sandstone, greywacke, and siltstone. The mineral composition and structure of the original rock have been changed due to contact metamorphism during the intrusion of the pluton, forming a complex of hornfels and granulites.

Zircon LA-MC-ICP-MS U-Pb dating of the two-mica granite, muscovite albite granite, albite pegmatite and albite spodumene pegmatite give crystallization ages of 219.2 ± 2.3 Ma (MSWD = 0.55), 217 ± 2.8 Ma (MSWD = 0.47), 202.8 ± 4.9 Ma (MSWD = 3.9), and 200.1 ± 4.6 Ma (MSWD = 3.1), respectively. The dating results of albite spodumene pegmatite samples can represent the age of rare-metal pegmatite veins, Lijiagou deposit was formed during the Late Triassic period and is closely related to the magmatic–hydrothermal activity of the Indosinian late stage [16,17]. The deposit is a Li-Cs-Ta (LCT) [18] spodumene-type pegmatite deposit with proven Li₂O resources of 512,185 tons and 15 orebodies in total. Generally, the length of individual orebodies ranges from 220 to 500 m, with a maximum of 2200 m; the thickness of orebodies is typically 5–10 m, up to 124 m. The orebodies are typically in the form of regular veins. Some are lenticular or layered and occur within pegmatite veins with medium length and greater thickness. The internal structure of the ore body does not exhibit distinct zonation, and there is a gradual transition between the ore-rich and ore-poor sections. Over 95% of rare metal ores are of the albite spodumene granite pegmatite type, with the remaining 5% being the albite lepidolite granite pegmatite type [19].

The ore exhibits relatively simple structural types, including massive structure, banded structure, disseminated structure, and miarolitic structure. The ore texture mainly consists of idiomorphic texture, semi-idiomorphic texture, xenomorphic texture, poikilitic texture, residual metasomatic texture, pseudomorphic texture, graphic texture, and crushed texture (Figure 2). The observed mineral assemblage on hand specimens includes spodumene, muscovite, quartz, feldspar, and minor amounts of pyrite, garnet, and tourmaline. Spodumene occurs as pale green or milky white crystals with semi-idiomorphic to idiomorphic prismatic or columnar shapes. The spodumene has a variable grain size (up to 2 cm). Metasomatic alteration and iron staining are commonly found in the ores.

3. Sampling and Analytical Methods

3.1. Sample

Most of the samples obtained for the current study were mined from the No. 1 ore body. Each core sample was 5–7 cm long, collected every 5.6 m at the middle part of the ore body, and one core sample of country rock was collected from the top and bottom of the vein for ore blending. A total of 93 samples (63 drill core samples and 30 grab samples) were collected for study. Samples were divided into four groups based on sampling location, whole rock Li content, and depth: LJG-1 (3857.78–3818.99 m), LJG-2 (3753.72–3710.44 m), LJG-3 (3739.45–3685.54 m), and LJG-4 (3702.53–3557.43 m) (Figure 3).

Thin sections and polished sections were prepared for petrographic observations and testing. The particle size of spodumene varied significantly, with larger grains exceeding 20 mm and smaller particles measuring only 0.01 mm. To ensure sample representativeness and reduce sampling errors, the original ore was crushed and fractionated. The samples were sieved into five size fractions—−2 mm, −0.6 + 0.25 mm, −0.25 + 0.106 mm, −0.106 + 0.075 mm, and −0.075 mm—for testing grain size distribution and liberation degree. Samples were crushed to simulate actual production conditions, the coarse crushing equipment used was the XPC-Φ100 × 60 jaw crusher, with a processing time of 2–3 min/kg. The fine crushing equipment used was the Φ200 × 125 double-roll crusher, with a processing time of 6–10 min/kg.

3.2. Whole-Rock Analyses

Whole-rock analyses of samples were performed at the Chengdu Institute for Multipurpose Utilization of Mineral Resources, CAGS. Geochemical analyses of samples were undertaken using a combination of standard mixed-acid digestion and peroxide fusion techniques for ICP-MS or ICP-OES spectrometry to determine the element and the Li abundances. X-ray powder diffraction studies were performed on ore samples using Cu Kα radiation on a Bruker D8 Advance diffractometer (Bruker Corporation, Billerica, MA, USA) with a graphite diffracted beam monochromator. Samples were pulverized followed by micronizing in ethanol to generate fine powders suitable for quantitative mineralogy analyses. The powders were backfilled into sample holders and pressed before scanning. Phase composition was determined using the search/match software Diffrac Eva with the ICDD powder diffraction database, the analysis was carried out on RIGAKU Ultima IV instrument (Rigaku Corp, Tokyo, Japan) running PDXL2 software. The voltage of the tube was set to 40 kV, tube current was 40 mA, and a scanning range of 5–65° was used with a 0.02° step size and a scanning rate of 5°/min; samples used for XRD quantitative analysis required crushing and compacting. Regarding SEM Automated Mineralogy (SEM-AM) methods for mineral liberation analysis (MLA), it was carried out at the Changsha Research Institute of Mining and Metallurgy using a FEI MLA650 resin in XBSE mode and a magnification of 300; relevant standards were referenced from Schulz et al., 2020 [20]. Sample preparation comprised cold inlaying with epoxy.

3.3. Mineralogical Analyses

Element analysis of mineral in thin sections were conducted with LA-ICP-MS at Nanjing FocuMS Technology Co., Ltd., Nanjing, China. A Teledyne Cetac Technologies Analyte Excite laser-ablation system (Teledyne Photon Machines, Bozeman, MT, USA) and an Agilent Technologies 7700× quadrupole ICP-MS (Hachioji, Tokyo, Japan) were combined for the experiments. The 193 nm ArF excimer laser, homogenized by a set of beam delivery systems, was focused on spodumene surface with fluence of 4.5 J/cm². Each acquisition incorporated 20 s background (gas blank), followed by spot diameter of 33 um at a 6 Hz repetition rate for 40 s. Helium (370 mL/min) was applied as carrier gas to efficiently transport aerosol out of the ablation cell and was mixed with argon (~1.15 L/min) via T-connector before entering ICP torch. Electron microprobe analysis was carried out with a SHIMADZU EPMA1720 (Shimadzu, Kyoto, Japan), using an accelerating voltage of 15 kV, tube current of 20 nA, and spot diameter of 10 μm.

4. Results

4.1. Ore Material Composition

4.1.1. Chemical Composition

Table 1. Results of chemical multivariate analysis.

Compositions		LJG-1	LJG-2	LJG-3	LJG-4
TFe	wt%	0.31	1.33	0.52	0.9
SiO2	wt%	76.86	69.18	74.28	71.69
Al2O3	wt%	14.42	17.42	14.83	15.87
Na2O	wt%	3.02	3.72	3.90	4.46
K2O	wt%	0.70	3.11	3.26	2.60
MgO	wt%	0.02	0.58	0.01	0.30
CaO	wt%	0.15	0.43	0.14	0.60
MnO	wt%	0.07	0.09	0.31	0.12
TiO2	wt%	0.03	0.25	0.02	0.03
Nb	ppm	209	175	140	210
Sn	ppm	-	-	529	-
TREO	ppm	10	110	9	53
Li	ppm	8100	2230	3500	2130
Rb	ppm	407	996	1720	1090
Cs	ppm	53	121	100	82
Be	ppm	72	71	96	82
Li2O	wt%	1.74	0.48	0.75	0.46

presents the elemental contents in four samples. The average SiO₂ content is 73.00%, Al₂O₃ content is 15.64%, and Na₂O + K₂O content is 6.20%. The Li₂O grade varied between 0.46 and 1.74% (average Li₂O% = 0.86), which is classified as low-grade ore, and the grade of LJG-1 is noticeably higher than the other three samples. No industrial value has been found for Nb-Ta, Sn, Be, Cs, and REE. The average content of Fe and Mn are 0.77% and 0.11%, and Fe + Mn content in LJG-3 and LJG-4 is relatively high. Overall, the ore grade of the Ljiagou deposit is comparable to that of other lithium deposits in the Ke’eryin rare metal ore field [21,22].

4.1.2. Mineralogical Composition

The samples are composed mainly of spodumene, muscovite, quartz, and albite. Most muscovite is type 3T. Polarizing microscopy is used to determine the mineralogical composition of different particle sizes of ore (Figure 4), and the results generally coincide with those determined with XRD (

Table 2. Mineral mode of ore in Lijiagou deposit obtained by XRD.

Types			Minerals	wt%
ore minerals			spodumene	11.3
			muscovite	12.17
gangue minerals	felsic minerals		albite, orthoclase, microcline, perthite, quartz, petalite	74.79
	accessory minerals	metallic minerals	columbite-tantalite, cassiterite, hematite, limonite, rhodochrosite, pyrite	0.24
		nonmetallic minerals	sericite, tourmaline, sphene, allanite, apatite, garnet, fluorite, chlorite, zircon, beryl	1.50

). As the muscovite is sheet-like, the analytically determined composition of mica minerals may be overestimated. In most samples, as the grinding particle size decreases, there is a slight reduction in the content of spodumene. Moreover, in the ore body, the spodumene content of samples from shallower depths is higher than in samples from deeper depths.

Dark-colored minerals are disseminated amongst the ores, with massive, speckled, and porphyritic appearances. These dark minerals are poorly crystallized, and most are found as aggregates embedded within mineral fractures. They were analyzed with XRD, which revealed that the dark-colored minerals are primarily composed of quartz and silicate minerals, including a significant presence of secondary minerals such as chlorite, illite, and serpentine. These minerals themselves have lighter colors, however, when they are assembled together in a certain form; this may lead to multiple scattering and absorption of light, resulting in the overall dark color of the aggregates.

4.2. Elements Occurrence

To ascertain the occurrence and distribution characteristic of lithium in ores, samples LJG-1, LJG-2, and LJG-3 were used for chemical phase analysis (

Table 3. Chemical phase analysis results of lithium.

Phase	Content (wt%)	Distribution (%)
Silicate	0.80	84.21
Mica	0.15	15.79
Total Li	0.95	100.00

). The distribution of lithium in two groups is consistent. Most lithium is distributed in silicate minerals. Approximately 84.1% of the total lithium is held in spodumene, and approximately 15.8% is in mica group minerals including muscovite, sericite, hydromica, and clay minerals in isomorphic form. A negligible amount of lithium is found in other minerals.

4.3. Spodumene Mineral-Processing Properties

4.3.1. Texture and Interlink Characteristic of Spodumene

Figure 5 presents the typical textures of the main minerals in the samples as observed under the microscope. Spodumene has a perfect {110} cleavage, two moderate cleavages in cross-section. Based on different degrees of metasomatism, spodumene is divided into two types. The first type displays idiomorphic to semi-idiomorphic platy and columnar habits with good crystal shape, with a grain size of 2–8 mm (Figure 5b). The second type displays metasomatic textures, and the particle size varies with the degree of metasomatism. The grain size of spodumene in the case of weak metasomatism is 0.3–3.5 mm. In the presence of intense metasomatic, spodumene displays residual replacement texture, with the grain size ranging 0.04–0.26 mm (Figure 5a2–a5).

The interlink characteristics of spodumene with other minerals are mainly divided into three types. The first type is characterized by contacts between idiomorphic spodumene and other minerals with relatively straight and distinct boundaries and is easily disassociated (Figure 5a1,b). The second type is characterized by contacts between spodumene and inclusions of other minerals or the replacement mineral in spodumene (Figure 5c). The inclusions range in size from 0.03 to 0.30 mm. The boundaries between minerals in this type are relatively complex and the grains are resistant to liberation. The third type mainly refers to the contact relation between spodumene and adjacent symplectites (Figure 5d–f). Symplectite is defined as an intimate intergrowth of two different minerals [23]. They are fine-grained mineral intergrowths developed in the process of secondary reaction or alteration. Spodumene of the present study has formed symplectites with quartz, feldspar, and muscovite, of which the spodumene–quartz symplectites are the most common. Spodumene exhibits a perfect cleavage and is easily liberated, but after the formation of symplectite, the connection between the vermicular spodumene and gangue minerals becomes tight, making it difficult to liberate. The recycling of spodumene from symplectites may be a research focus in the future.

4.3.2. Chemical Composition of Spodumene

In any chemical process for decomposing spodumene and extracting lithium, it is necessary to manage the mineral and elemental impurities present. Generally, spodumene with higher Fe content is light green in color, while that with a low Fe content is white or light grey [24]. The chemical composition of spodumene is relatively stable: there is no Al to replace Si in the Si-O tetrahedron, and small amounts of Fe and Mn often replace Al in six-fold coordination; Na, K, and Ca often replace Li. The average chemical composition of spodumene is listed in

Table 4. Average chemical composition of spodumene and standard derivation from LA-ICP-MS analysis.

Compositions	Units	Average	Max	Min	SD
Na2O	wt%	0.11	0.15	0.07	0.03
MgO	wt%	0.00	0.00	0.00	0.00
Al2O3	wt%	28.24	29.49	25.39	1.28
SiO2	wt%	64.86	68.32	63.60	1.50
P2O5	wt%	0.02	0.04	0.00	0.01
K2O	wt%	0.01	0.02	0.00	0.01
CaO	wt%	0.04	0.13	0.00	0.04
TiO2	wt%	0.00	0.01	0.00	0.00
MnO	wt%	0.08	0.12	0.04	0.03
FeO	wt%	0.19	0.31	0.11	0.07
Li2O	wt%	6.40	6.81	5.97	0.30

. The content of impurities such as Fe, Mn, and P are low, and the content of Li₂O ranged from 5.97% to 6.81%, with an average of 6.40%, which is the theoretical grade of lithium concentrate and classified as a chemical-grade lithium product.

4.3.3. Particle Size Distribution

Particle size testing of spodumene was conducted on the −2 mm ore (Figure 6). LJG-1 has a particle size range of 0–1548 μm, and nearly 90 wt% of the total was −200 µm. The particle size characteristics of LJG-2 and LJG-3 are similar. The particle size ranges are 0–857 μm and 0–929 μm, and approximately 89 wt% of the total was −100 µm. Compared to other samples, the particle size distribution of LJG-4 is slightly concentrated, and 86 wt% of the total was −100 µm. On the whole, the samples belong to extremely heterogeneous ores, with a wide range of granularities and similar spodumene contents in each size class, making it difficult to determine the appropriate grinding fineness.

4.3.4. Spodumene Liberation

Mineral liberation describes the degree to which a mineral of interest is liberated from other minerals. In this study, liberation was classified based on the surface area of spodumene. "Liberated," indicating complete separation with a liberation degree of 100%; "Mostly Liberated," signifying that the majority of mineral particles are separated (liberation degree typically ranging from 75% to 100%); "Middling," indicating a moderate level of liberation, with liberation degrees falling between 25% and 75%; and "Locked," suggesting very little liberation, with liberation degrees below 25%. The dissociation results of each sample within the size ranges of −0.6 + 0.25 mm, −0.25 + 0.106 mm, −0.106 + 0.075 mm, and −0.075 mm are shown in Figure 7. The liberation characteristics of the four samples are generally the same: spodumene is concentrated in the liberated and mostly liberated classes. For LJG-2, LJG-3, and LJG-4, there is a significant variation in spodumene liberation across different particle sizes, ranging from approximately 40% in the coarser size fraction to 92% in the finer size fractions. As the particle size decreases, the liberation of spodumene increases. Within the particle size range of −0.075 mm, the liberation of spodumene in almost all samples can reach 90% or more. In this light, grinding ore to a finer particle size is more conducive to the liberation of spodumene. Moreover, the liberation of spodumene is correlated with the depth, with shallower sampling locations exhibiting higher levels of spodumene liberation.

5. Discussion

The fundamental reason for the low quality of spodumene concentrate products is the low Li content of spodumene itself. In the mineral formula of pyroxene (XYZ₂O₆), X represents Na, Ca, Mn, Fe, Mg, and Li in the distorted 6- to 8-coordinated M2 site; Y represents Mn, Fe, Mg, Al, Cr, and Ti in the octahedral Ml site; and Z represents Si and Al in the tetrahedral site. As shown in Figure 8, Li₂O% in spodumene from the Lijiagou deposit is less than that from other deposits.

The vermicular elongated spodumene grains in the symplectites have a size range of 3 to 50 μm, with the majority being smaller than 20 μm, and the Li₂O% is similar to that of the idiomorphic spodumene. Li₂O% in symplectites is 1.88%–6.24% with an average of 3.40%. As depicted in Figure 9c, even when the vermicular elongated spodumene is ground into smaller particles, it should still retain its elongated morphological characteristics. By selecting spodumene grains with sizes smaller than 20 μm from the MLA color images and arranging them from largest to smallest (Figure 9a), a comparison reveals that the number of elongated spodumene grains in the MLA color images is significantly insufficient. Due to the limitations of the beam size, conventional MLA has difficulty accurately identifying tiny vermicular spodumene, and vermicular elongated spodumene is challenging to separate from gangue minerals. Therefore, vermicular spodumene is prone to being misidentified as gangue minerals and lost to the tailings.

In addition, the abundant development of symplectites and the sericitization in the ore indicate that the deposit has undergone intense alteration. The alteration effects of late-stage hydrothermal fluids on the ore are one of the key factors influencing the ore grade and lithium recovery. This influence is particularly pronounced in the deep portions of the deposit. Secondary quartz and albite have replaced the idiomorphic spodumene, and the degree of replacement is directly related to the size of the spodumene grains. Higher degrees of replacement result in smaller spodumene grain sizes, thus affecting the spodumene granularity. The Li₂O% content in the core of muscovite ranges from 0.21% to 2.22%, with an average of 1.03%. The Li₂O% content at the rim can reach up to 3.5%. The edge Li₂O% of spodumene is slightly lower than that of the core, with an average value of approximately 6.18%. Under BSE imaging (Figure 10), it can be observed that the composition of muscovite is not uniform, and the color of the rim is visibly distinct from that of the core. Spodumene typically exhibits lithium depletion at the edges, while muscovite edges show enrichment in lithium; it is highly likely that the interaction between the late-stage hydrothermal fluids and spodumene involves material exchange, leading to the loss of some lithium. As a result, the content of spodumene and Li₂O% in the deep-seated ore is relatively low. During the process of alteration, spodumene forms symplectites with other minerals at its edges, leading to a decrease in the proportion of easily dissociable interlink types. As a result, the dissociation degree of spodumene is reduced.

Under geological stress, spodumene is prone to develop fractures. Clay minerals such as chlorite and illite infiltrate spodumene along these fractures, leading to an increase in impurity, Fe content, in the concentrate product. Clay minerals have a large specific surface area, which results in the adsorption of a significant amount of reagents during the flotation process, leading to reagent wastage. Additionally, clay minerals may release Fe³⁺, Al³⁺, Ca²⁺, Mg²⁺, which have a strong activating effect on other minerals. This effect causes spodumene and gangue minerals to have similar floatability, thereby increasing the difficulty of flotation separation. Therefore, to ensure the quality of lithium concentrate, it is necessary to pay attention to the desliming process.

Based on the anisotropy theory for crystal surface properties of pegmatite-type aluminosilicate minerals, it was found that the spodumene with coarser granularity (0.074–0.038 mm) had maximum floatability, while the floatability of gangue minerals, including albite, was at a maximum with relatively fine granularity (−0.038 mm) [28]. Meanwhile, to achieve a minimum of 90% complete dissociation of spodumene, it is recommended to grind the material to a particle size of less than 0.075 mm before entering the final flotation process. This particle size range is considered optimal to ensure effective separation and recovery of spodumene during flotation, and the recommended particle size for the first stage of grinding is around 0.15 mm.

Overall, the ore from Lijiagou is characterized by heterogeneity and a wide range of particle sizes. Therefore, it is recommended to adopt a multi-stage grinding and multi-stage separation process based on the specific circumstances. The flotation test design proposed by Xu for the pegmatite-type spodumene in Western Sichuan can be used as a reference [12]: adopt the process flow of primary grinding → coarse mica flotation → tailings regrinding → desliming → fine spodumene flotation process for spodumene beneficiation.

6. Conclusions

(1)

Ljiagou spodumene deposit lithium ore grade is 0.86%, which is considered low-grade lithium ore. The theoretical grade of lithium concentrate is 6.4%.

(2)

Recovering Li from symplectitic spodumene–quartz intergrowths is hampered by considerable difficulties, as it is prone to being entrained in the tailings during the separation process.

(3)

The process characteristics of the ore are controlled by elevation and, overall, exhibit a heterogeneous nature. It is recommended to employ a multi-stage grinding and multi-stage beneficiation process, while also incorporating a desliming step. It is best to maintain the particle size of the first-stage grinding at around 0.15 mm, and, prior to entering the final flotation process, the material should be ground to a size of less than 0.075 mm.