A highly ordered Ge-incorporated akaganeite with the atomic ratio of Ge/Fe = 0.14 and Cl/Fe = 0.11 was firstly synthesized through hydrolysis and acidification of a mixed solution of FeCl₃·6H₂O and TEOGe (Ge(OC₂H₅)₄) under the α-Fe₂O₃ synthesis conditions. The newly synthesized Ge-akaganeite shows a monodisperse nanorod with 15–17 nm in width and ∼200 nm in length, the distinctly enhanced structural ordering and stability, and substantial differences in crystallographic and magnetic features. Here we propose a hypothetical akaganeite model with Ge occupying the tunnel sites as Ge(OH)₄ ⁰ based on crystallographic and chemical analyses.

Phengite series is a dioctahedral solid solution between two end-members of muscovite [K₁[Al₂]^VI[Al₁,Si₃]^IVO₁₀(OH)₂] and celadonite [K₁[(Fe³⁺,Al)₁,(Mg,Fe²⁺)₁]^VI[Si₄]^IVO₁₀(OH)₂], which have a hetero-valent substitution of Al^VIAl^IV ↔ (Mg, Fe)^VISi^IV. In this study, we report a hydrothermal-originated authigenic Mg-phengite-series mineral, which occurred as polycrystalline aggregates (Type 1), pore-fillings (Type 2) and well-crystallized lath form (Type 3) from the Haengmae Formation, a dolomite–pebble-bearing fine sand-sized dolostone, in South Korea. Based on micro-textural observation, three types of Mg-phengite are associated with crystalline dolomite, and are followed by calcite precipitation as pore-filling, indicating that these should be formed by the influx of a Mg-rich hydrothermal fluid after the deposition of some clastic sediments and before calcite-filling. The structural formula based on O₁₀(OH)₂ shows that the number of Mg atoms per formula unit (apfu) of Mg-phengite ranges from 0.00 to 0.70 with no Fe, which is relatively high, compared with the previously reported metamorphic phengites. In REEs mineral chemistry, the Mg-phengites are characterized by the enrichment of REEs and by the particular enrichment of LREEs in the polycrystalline aggregates of Mg-phengite. It strongly suggests that the Mg-phengite should be formed by the infiltration of the highly evolved Mg- and REEs-enriched hydrothermal fluid into the clastic sedimentary rock (Haengmae Formation) as a strata-bound form, syngenetically or during early diagenesis.

Ordered single-walled hollow aluminogermanate (ALGE) nanospheres (NSs) with average monodisperse diameters of 5 nm have been synthesized for the first time using simple pH control. This involved basification of the ALGE precursors (having an Al/Ge ratio of 1.33) to a pH value of 13, followed by immediate acidification to a pH value of 9.