Alumogel

Alumogel is not a formally recognized mineral species but rather an obsolete name applied to ill‑defined, gel‑like hydrous aluminum oxides. It is best thought of as a transitional or amorphous phase related to minerals like allophane and aluminite.

🌍 Origins and Naming

• Name Origin: From alum (aluminum) + gel, describing its soft, gelatinous appearance.
• Status: Not approved by the International Mineralogical Association (IMA).
• Historical Context: Used in older literature to describe fine-grained, hydrated aluminum oxides found in bauxite deposits and oxidation zones.

🔬 Chemical and Structural Properties

• Composition: Hydrous aluminum oxides, poorly defined.
• Structure: Amorphous or gel-like; lacks long-range crystallinity.
• Appearance: White to pale earthy masses, often resembling clays or gels.
• Associations: Frequently occurs with aluminite (Al₂SO₄(OH)₄·7H₂O) and allophane (Al₂O₃·(SiO₂)₁.₃–₂·2.5–3H₂O).

⚙️ Geological Occurrence

• Found in bauxite deposits and oxidized ore zones, where aluminum-bearing minerals undergo hydration and alteration.
• Localities: Reported from Zlaté Hory, Jeseník District, Olomouc Region, Czech Republic.
• Formation: Secondary product of weathering and alteration of aluminum-rich rocks.

📖 Scientific and Collector Significance

• Petrology: Illustrates transitional phases between crystalline aluminum hydroxides (like gibbsite) and amorphous aluminosilicates (like allophane).
• Collectors: Rarely collected; specimens are usually unattractive earthy masses.
• Modern Status: Considered a non-species or descriptive term rather than a valid mineral.

✨ Conclusion

Alumogel is an obsolete descriptive name for gel-like hydrous aluminum oxides, typically found in bauxite or oxidized deposits. It is scientifically interesting as a transitional phase but has no standing as a distinct mineral species today.

In short: Alumogel = obsolete name, gel-like hydrous aluminum oxides, related to allophane and aluminite, found in bauxite deposits.

Sources:

You can explore more details on Mindat’s alumogel entry.