Abstract

The Lembo clay deposit occurs on orthogneiss, but it also comprises clays with lithorelicts of volcanic rocks. In this study, ten samples from two sites were investigated. The mineralogical compositions consisted of kaolinite + halloysite + illite + quartz + hematite + anatase 3 rutile 3 orthoclase 3 sanidine 3 magnetite 3 maghemite 3 goethite 3 Ba-Al-Fe-phosphates 3 carbonates 3 sulphates. Kaolinite-halloysite and quartz are the prevailing minerals. Some volcanic-derived clays contain Fe-rich kaolinite-halloysite (9.6–14.1 wt.% Fe2O3). The chemical compositions, colours and specific surface area (SSA) measurements reveal two groups of clays: one with a positive whiteness index (IB), small SSA and small Fe content, and the other showing a large SSA, negative IB and relatively large Fe contents. The compositions of the first group are close to those of clays from the Mayouom deposit (Cameroon), and from some European commercial kaolins used in ceramics. Relatively Fe-rich clay materials may conform to most formulations of earthen bricks. As a whole, the Lembo clay deposit comprises various compositions of kaolinitic clays, which may yield the opportunity for extensive application in ceramics.

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