Aluminite

Aluminite is a rare hydrous aluminum sulfate mineral, Al₂SO₄(OH)₄·7H₂O. It is soft, earthy, and typically forms as a secondary mineral in oxidized environments.

🌍 Origins and Naming

• Name Origin: From its aluminum content.
• Discovery: First described in 1807.
• Type Locality: Likely from England, where early specimens were studied.

🔬 Chemical and Structural Properties

• Formula: Al₂SO₄(OH)₄·7H₂O
• Mineral Group: Sulfates.
• Crystal System: Monoclinic (though crystals are extremely rare; usually earthy masses).
• Color: White, grayish, sometimes pale yellow.
• Habit: Earthy, clay-like masses; rarely fibrous or compact.
• Hardness: ~1.5–2 on Mohs scale (very soft).
• Specific Gravity: ~1.7–1.8 (light due to hydration).
• Luster: Dull to earthy.
• Streak: White.

⚙️ Geological Occurrence

• Forms as a secondary mineral in clay deposits, lignite beds, and oxidized sulfide veins.
• Associated Minerals: Gibbsite, alunogen, gypsum, halotrichite, and other hydrated sulfates.
• Localities:
  • England (classic occurrences).
  • Germany.
  • USA (notably in coal-bearing regions).

📖 Scientific and Collector Significance

• Petrology: Illustrates hydration and alteration processes of aluminum-bearing sulfates.
• Collectors: Rarely aesthetic; valued academically for its rarity and paragenesis.
• Industrial Note: No commercial use; too soft and unstable.

✨ Conclusion

Aluminite is a soft, hydrous aluminum sulfate, usually forming earthy white masses in oxidized environments. It is scientifically interesting as a secondary mineral but remains a collector’s curiosity rather than an economic resource.

In short: Aluminite = Al₂SO₄(OH)₄·7H₂O, soft earthy sulfate, rare, first described in 1807.