Critical elements in coal deposits, such as lithium (Li), have attracted attention recently due to their economic value. Many studies have suggested that the high enrichment of Li in coals is predominantly associated with cookeite, a Li–bearing chlorite mineral of hydrothermal origin. However, the identification of cookeite in coal has primarily relied on indirect methods, owing to the low atomic number of Li, which presents significant challenges for precise observation. The Shanxi Formation No. 2₁ coal in North China is enriched in Li. This study established a nanometer–scale mineralogical analytical technique (including high–resolution transmission electron microscopy (HR–TEM), fast Fourier transformation (FFT), and standard mineral simulation single-crystal diffraction (SSCD)) for the identification of the cookeite and evaluated the Li enrichment mechanism and recovery in this coal (low–volatile bituminous to semi–anthracite) based on a model for the Li mineralization. The Li content of the No. 2₁ coal ranges from 25.2 to 203 ppm. The Li content shows a strong correlation with the ash yield, Al₂O₃, SiO₂, and detrital elements, indicating a dominant aluminosilicate affinity and detrital origin. The major aluminosilicate minerals in coal are kaolinite, chlorite, and illite. The geochemical indicators (the Al₂O₃/TiO₂ ratio and its relationships with the Zr/TiO₂, Nb/Y, and Nb/Yb ratios) indicate that the sediment sources are determined to be intermediate–felsic igneous rocks, probably the Mesoproterozoic moyite (a type of K– feldspar granite) in the Yinshan Oldland. Additionally, the coal can be divided vertically into three sections (Sections I, II, and III), corresponding to three stages of peat formation. Overall, from Section I to Section III, the degree of detrital input increased, and the groundwater and marine influences strengthened and weakened, respectively. Section II exhibits anomalous Li enrichment mainly associated with reducing environments and the geochemical barrier caused by the interaction between infiltrating seawater and groundwater. The detrital kaolinite assemblage with authigenic minerals such as secondary REE–rich minerals (bastnasite), chamosite, and quartz, as well as the REY enrichment patterns, suggests that the No. 2₁ coals, mainly Section II, may have existed the hydrothermal alteration. Cookeite is identified primarily in Section II and coexists with kaolinite based on TEM observations, suggesting that the cookeite is of hydrothermal origin and formed from pre–existing Li–rich kaolinite. Most samples from Section II meet the mining grade of Be–Li–Nb–Ta ore deposits (Li₂O > 0.2%). Thus, this study offers valuable insights into the extraction and recovery of Li from coal combustion residues, particularly when cookeite is the primary Li–bearing mineral.

煤矿中的关键元素，例如锂（Li），最近因其经济价值而引起人们的关注。许多研究表明，煤中锂的高富集主要与钙石英有关，这是一种热液成因的含锂绿泥石矿物。然而，由于Li的原子序数较低，煤炭中cocoteite的识别主要依赖于间接方法，这对精确观测提出了重大挑战。华北山西组2 _{1号煤富集于李。}本研究建立了一种纳米级矿物学分析技术（包括高分辨率透射电子显微镜（HR-TEM）、快速傅立叶变换（FFT）和标准矿物模拟单晶衍射（SSCD）），用于鉴定库硅石和基于锂矿化模型评估了这种煤（低挥发性烟煤到半无烟煤）中锂的富集机制和回收率。_{2· 1号煤}的Li含量为25.2～203ppm。Li含量与灰分产量、Al ₂ O ₃、SiO ₂和碎屑元素有很强的相关性，表明主要的铝硅酸盐亲和力和碎屑来源。煤中的主要铝硅酸盐矿物是高岭石、绿泥石和伊利石。地球化学指标（Al ₂ O ₃ /TiO ₂比值及其与Zr/TiO ₂ 、Nb/Y、Nb/Yb比值的关系）表明沉积物来源为中长英质火成岩，可能是阴山古陆中元古代闪辉岩（钾长石花岗岩的一种）。此外，煤可垂直分为三个部分（I、II 和 III 部分），对应于泥炭形成的三个阶段。总体而言，从Ⅰ段到Ⅲ段，碎屑输入程度加大，地下水和海洋影响分别增强和减弱。第二部分展示了锂的异常富集，主要与还原环境和渗透海水与地下水之间相互作用引起的地球化学屏障有关。碎屑高岭石与富稀土次生矿物（氟碳铈矿）、硅铜矿、石英等自生矿物的组合以及REY富集模式表明，以II段为主的2号₁煤可能存在热液蚀变。。根据 TEM 观察，库克石主要在第二部分中被识别出来，并与高岭石共存，表明库克石是热液成因，由预先存在的富锂高岭石形成。第二部分的大多数样品满足 Be-Li-Nb-Ta 矿床的开采品位（Li ₂O > 0.2%）。因此，这项研究为从煤燃烧残渣中提取和回收锂提供了宝贵的见解，特别是当硅酸锂是主要含锂矿物时。