Alunogen

Alunogen is a hydrated aluminum sulfate mineral, Al₂(SO₄)₃·17H₂O. It is one of the most water-rich sulfates known, forming delicate fibrous crystals in oxidized environments.

🌍 Origins and Naming

• Name Origin: From alum (due to its sulfate chemistry) + -gen (“producer”), reflecting its relation to alum salts.
• Discovery: First described in the early 19th century.
• Type Locality: Likely from European mining districts where sulfide ores oxidize.

🔬 Chemical and Structural Properties

• Formula: Al₂(SO₄)₃·17H₂O
• Mineral Group: Sulfates.
• Crystal System: Triclinic.
• Color: Colorless to white; sometimes pale yellow or pink.
• Habit: Fine fibrous crystals, crusts, or efflorescences.
• Hardness: ~1.5–2 on Mohs scale (very soft).
• Specific Gravity: ~1.7–1.8 (light due to high hydration).
• Luster: Silky to vitreous.
• Streak: White.

⚙️ Geological Occurrence

• Formation: Secondary mineral formed by oxidation of sulfide ores (especially pyrite).
• Environment: Found in mine walls, dumps, and oxidized zones where acidic waters evaporate.
• Associated Minerals: Halotrichite, pickeringite, melanterite, gypsum, aluminite.
• Localities:
  • Freiberg, Saxony, Germany.
  • Numerous mining districts in Europe and North America.

📖 Scientific and Collector Significance

• Petrology: Indicator of highly acidic, sulfate-rich environments.
• Collectors: Attractive silky fibrous crystals can be delicate but prized; often ephemeral due to instability.
• Industrial Note: No commercial use; mainly of academic and collector interest.

✨ Conclusion

Alunogen is a highly hydrated aluminum sulfate, forming silky fibrous crystals in oxidized sulfide deposits. It is scientifically important as an indicator of acid mine environments and prized by collectors for its delicate appearance, though it is unstable and has no industrial role.

In short: Alunogen = Al₂(SO₄)₃·17H₂O, fibrous hydrated sulfate, secondary mineral in oxidized sulfide zones.