bauxiitti

Bauxiitti is a proposed aluminum oxide–hydroxide mineral identified in some tropical laterite and bauxite deposits. The name appears in a limited body of literature as a hydrated aluminum phase distinct from the better-known minerals gibbsite, boehmite, and diaspore. The nominal composition is Al2O3·nH2O, with hydration level n typically ranging from 1 to 3 and with trace impurities such as Fe, Ti, Si, and Na.

Formation and occurrence: Bauxiitti is thought to form during intense tropical weathering of aluminous rocks, through dehydration of primary aluminum hydroxide minerals and accumulation within lateritic deposits. It is most commonly reported in near-surface zones where leaching concentrates aluminum-bearing compounds, often coexisting with other bauxite constituents.

Physical characteristics: It is usually microcrystalline to earthy, lacking distinctive cleavage, with a dull to pearly luster. Color ranges from white to pale yellow or brown. X-ray diffraction often shows broad, poorly defined peaks consistent with low crystallinity; microprobe analyses indicate high aluminum content with variable impurities. The phase is typically identified by its hydrated nature rather than a well-crystallized structure.

Economic and geological significance: As a hydration-rich aluminum phase, bauxiitti is generally considered a secondary constituent in bauxite deposits rather than a primary ore mineral. During aluminum refining, it can be converted to more stable phases such as gibbsite or boehmite under processing conditions.

Taxonomic status and nomenclature: Bauxiitti is not widely recognized as an official mineral species by major nomenclature authorities, and its usage is mostly confined to regional or preliminary reports. The name derives from its association with bauxite and its hydrated oxide composition.