Agardite is a rare group of hydrated copper rare-earth arsenate minerals, notable for their vivid green to blue colors and fibrous habit. It belongs to the mixite group and is scientifically important for understanding secondary mineral formation in arsenic-rich environments.
🌍 Origins and Naming
- Name Origin: Named in 1960 after French mineralogist Jules Agard (1912–2001).
- Mineral Group: Mixite group (complex Cu–REE arsenates).
- Type Locality: Cap Garonne mine, Le Pradet, Var, France.
🔬 Chemical and Structural Properties
- General Formula: (REE,Ca)Cu₆(AsO₄)₃(OH)₆·3H₂O
- REE = rare earth elements (commonly Y, Ce, La, Nd).
- Crystal System: Hexagonal
- Color: Bright green, bluish-green, sometimes turquoise
- Habit: Fibrous, acicular, or radial sprays; crusts and coatings on host rock
- Hardness: ~3–4 on Mohs scale
- Specific Gravity: ~3.8–4.0
- Luster: Silky to vitreous
- Streak: Pale green
⚙️ Geological Occurrence
Agardite forms as a secondary mineral in the oxidation zones of copper-arsenic deposits.
- Associated Minerals: Mixite, malachite, azurite, olivenite, erythrite.
- Localities:
- Cap Garonne mine, France (classic locality)
- Laurium, Greece
- Tsumeb, Namibia
- Cornwall, England
- USA (Arizona, Nevada)
📖 Scientific and Collector Significance
- Petrology: Indicator of arsenic-rich oxidation environments.
- Collectors: Attractive fibrous sprays and vivid colors make it desirable, though specimens are often delicate.
- Varieties:
- Agardite-(Y) – yttrium-dominant
- Agardite-(Ce) – cerium-dominant
- Agardite-(La) – lanthanum-dominant
- Agardite-(Nd) – neodymium-dominant
⚠️ Safety Considerations
Agardite contains arsenic, so handling requires care. Wash hands after contact and avoid inhaling dust.
✨ Conclusion
Agardite is a rare copper-REE arsenate mineral with striking green fibrous crystals, scientifically valuable for understanding secondary mineralization and prized by collectors for its beauty. Its multiple REE-dominant varieties highlight the complexity of arsenate mineral chemistry.
In short: Agardite is a vivid green copper-rare earth arsenate mineral, found in oxidized copper deposits.
