Aguilarite is a rare silver sulfosalt mineral, chemically a silver selenide-sulfide, and part of the acanthite–naumannite series. It is scientifically important because it represents the selenium-rich endmember of this series, bridging silver sulfide (Ag₂S) and silver selenide (Ag₂Se).
🌍 Origins and Naming
- Name Origin: Named in 1891 after P. Aguilar, a mine director in Guanajuato, Mexico, where the mineral was first described.
- Type Locality: Guanajuato mining district, Mexico.
🔬 Chemical and Structural Properties
- Formula: Ag₄SeS (sometimes written as Ag₂S·Ag₂Se)
- Mineral Group: Sulfosalts (silver selenide-sulfide series)
- Crystal System: Monoclinic
- Color: Dark gray to black, metallic
- Habit: Typically massive or granular, rarely well-formed crystals
- Hardness: 2–2.5 on Mohs scale (very soft)
- Specific Gravity: ~6.7–6.9 (very dense due to silver content)
- Luster: Metallic
- Streak: Black
⚙️ Geological Occurrence
Aguilarite occurs in hydrothermal silver deposits, often associated with other silver minerals.
- Associated Minerals: Acanthite (Ag₂S), naumannite (Ag₂Se), proustite, pyrargyrite, galena, chalcopyrite.
- Localities:
- Guanajuato, Mexico (type locality)
- Other silver-rich deposits in Germany, Chile, and the USA (Colorado, Nevada).
📖 Scientific and Collector Significance
- Petrology: Important for understanding selenium substitution in silver sulfide systems.
- Collectors: Rare and usually unattractive visually (dark metallic masses), but valued for rarity.
- Economic Note: Minor ore of silver, though not a major commercial source due to scarcity.
⚠️ Safety Considerations
Contains selenium, which can be toxic in high concentrations. Handling requires care, though risk is minimal for solid specimens.
✨ Conclusion
Aguilarite is a rare silver selenide-sulfide mineral, first described in Mexico, scientifically significant as the selenium-rich endmember of the acanthite–naumannite series. While not visually striking, it is prized by collectors and mineralogists for its rarity and geochemical importance.
In short: Aguilarite is a rare silver sulfosalt (Ag₄SeS), bridging silver sulfide and silver selenide, first found in Guanajuato, Mexico.
