Large kaolin deposits developed by weathering on Precambrian granitic rocks have been discovered in the Caluquembe area, Huíla province, Angola. To determine accuracy of analysis and to evaluate the kaolinite grade, a full-profile Rietveld refinement by X-ray Powder Diffraction (XRPD) and Thermal Gravimetric Analysis (TGA) was used. Caluquembe kaolin is composed mainly of kaolinite (44–93 wt.%), quartz (0–23 wt.%), and feldspar (4–14 wt.%). The Aparicio-Galán-Ferrell index (AGFI), calculated by XRPD profile refinement, indicates low- and medium-defect kaolinite. Kaolinite particles show a platy habit and they stack together forming ‘booklets’ or radial aggregates; they also occur as small anhedral particles in a finer-grained mass. Muscovite-kaolinite intergrowths have also been found. Whole-rock chemical analysis included major, trace, and Rare Earth Elements (REE). Chondrite-normalized REE patterns show the same tendency for all samples, with a significant enrichment in Light Rare Earth Elements (LREE). Mineralogical and compositional features of the Caluquembe kaolin indicate that it is a suitable material for the manufacture of structural products, such as bricks, paving stones, and roofing tiles. In addition, the significant REE contents of the Caluquembe kaolin can be considered as a potential future target of mining exploration.

中文翻译：

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西非新高岭土矿床：来自 Caluquembe（安哥拉）的高岭石的矿物学和成分特征

在安哥拉威拉省的卡卢肯贝地区发现了在前寒武纪花岗岩上风化形成的大型高岭土矿床。为了确定分析的准确性并评估高岭石等级，使用了通过 X 射线粉末衍射 (XRPD) 和热重分析 (TGA) 进行的全剖面 Rietveld 细化。Caluquembe 高岭土主要由高岭石 (44–93 wt.%)、石英 (0–23 wt.%) 和长石 (4–14 wt.%) 组成。Aparicio-Galán-Ferrell 指数 (AGFI)，通过 XRPD 轮廓细化计算，表明低和中缺陷高岭石。高岭石颗粒呈片状，堆积在一起形成“小册子”或放射状聚集体；它们也以细粒度的小正面体粒子的形式出现。还发现了白云母-高岭石共生体。全岩化学分析包括主要、痕量、和稀土元素 (REE)。球粒陨石归一化 REE 模式显示所有样品的相同趋势，轻稀土元素 (LREE) 显着富集。Caluquembe 高岭土的矿物学和成分特征表明它是制造结构产品的合适材料，例如砖、铺路石和屋面瓦。此外，Caluquembe 高岭土的显着 REE 含量可被视为未来采矿勘探的潜在目标。和屋顶瓦片。此外，Caluquembe 高岭土的显着 REE 含量可被视为未来采矿勘探的潜在目标。和屋顶瓦片。此外，Caluquembe 高岭土的显着 REE 含量可被视为未来采矿勘探的潜在目标。