Alluaudite

Alluaudite is a rare phosphate mineral, part of the triphylite–lithiophilite group, notable for its complex chemistry and occurrence in granitic pegmatites.

🌍 Origins and Naming

• Name Origin: Named after French naturalist François Alluaud (1778–1866).
• Discovery: First described in 1848.
• Type Locality: Skardu, Gilgit-Baltistan, Pakistan (though early descriptions also reference French localities).

🔬 Chemical and Structural Properties

• Formula: (Na,Ca)(Fe²⁺,Mn²⁺)₂(Fe³⁺,Mn³⁺)(PO₄)₃
• Mineral Group: Phosphates (alluaudite group).
• Crystal System: Monoclinic.
• Color: Black, brownish-black, sometimes greenish-black.
• Habit: Massive, granular; crystals are rare.
• Hardness: ~5–5.5 on Mohs scale.
• Specific Gravity: ~3.5–3.6.
• Luster: Submetallic to vitreous.
• Streak: Brownish-black.

⚙️ Geological Occurrence

• Found in granitic pegmatites and phosphate-rich environments.
• Associated Minerals: Triphylite, lithiophilite, vivianite, heterosite, and other phosphates.
• Localities:
  • Skardu, Pakistan.
  • Varuträsk, Sweden.
  • Hagendorf, Germany.
  • Other pegmatite localities worldwide.

📖 Scientific and Collector Significance

• Petrology: Important for understanding phosphate mineralization in pegmatites.
• Collectors: Rare, usually massive and dark-colored, valued for its rarity and association with classic pegmatite localities.
• Economic Note: No industrial use; mainly of academic and collector interest.

✨ Conclusion

Alluaudite is a complex phosphate mineral first described in the mid-19th century, found in pegmatites and phosphate-rich deposits. It is scientifically significant for illustrating phosphate mineral chemistry, though it remains a collector’s curiosity rather than an economic resource.

In short: Alluaudite = phosphate mineral, dark-colored, rare, first described in 1848, found in pegmatites.