Ahlfeldite is a rare nickel selenite mineral, part of the selenite group, and notable for its bright green coloration. It is scientifically interesting because it represents nickel’s incorporation into selenium-bearing secondary minerals, typically forming in the oxidation zones of nickel-selenium deposits.
🌍 Origins and Naming
- Name Origin: Named in 1950 after Dr. Friedrich Ahlfeld (1892–1982), a German geologist known for his work in South America.
- Type Locality: Sierra de Cachimbo, Bolivia.
🔬 Chemical and Structural Properties
- Formula: NiSeO₃·2H₂O
- Mineral Group: Selenites
- Crystal System: Monoclinic
- Color: Bright emerald-green to bluish-green
- Habit: Fibrous crusts, earthy coatings, or fine-grained aggregates
- Hardness: ~2–3 on Mohs scale (soft)
- Specific Gravity: ~3.8–4.0
- Luster: Vitreous to silky
- Streak: Greenish
⚙️ Geological Occurrence
Ahlfeldite forms as a secondary mineral in the oxidation zones of nickel-selenium deposits.
- Associated Minerals: Chalcomenite (Cu selenite), cobaltomenite (Co selenite), and other secondary selenium minerals.
- Localities:
- Bolivia (type locality)
- Chile
- Argentina
- Rare occurrences in other selenium-rich deposits worldwide
📖 Scientific and Collector Significance
- Petrology: Provides insight into selenium geochemistry and nickel’s role in secondary mineral formation.
- Collectors: Attractive green coloration makes it desirable, though specimens are rare and often small.
- Economic Note: Not an ore of nickel or selenium due to rarity, but scientifically valuable.
⚠️ Safety Considerations
Contains selenium, which can be toxic. Handling requires care—avoid inhaling dust or ingesting particles, and wash hands after contact.
✨ Conclusion
Ahlfeldite is a rare nickel selenite mineral, first described in Bolivia, valued for its vivid green color and scientific importance in understanding selenium-rich oxidation environments. Though not economically significant, it remains a collector’s curiosity and a geochemical marker.
In short: Ahlfeldite is a rare green nickel selenite, first found in Bolivia, prized for rarity and scientific value.
