Argentobaumhauerite
Chemical formula: Ag<sub>1.5</sub>Pb<sub>22</sub>As<sub>33.5</sub>S<sub>72</sub>
Argentobaumhauerite is a rare sulfosalt of lead, silver, and arsenic, forming opaque, metallic, dark gray crystals.
Properties
- Mohs hardness
- 3
- Luster
- Metallic
- Streak
- Red-brown
- Density
- 5.39
- Cleavage
- Perfect on {100}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Triclinic
Diagnostic features
## Identification Amateur identification of argentobaumhauerite is practically impossible. It requires advanced analytical methods, such as chemical composition analysis (EDS/WDS) and X-ray diffraction (XRD). Preliminary identification is based on its dark gray color, metallic luster, and co-occurrence with other rare sulfosalts in its type locality. ## Distinguishing from Similar Minerals It can be confused with many other lead sulfosalts, such as baumhauerite, sartorite, dufrenoysite, or jordanite, which often occur together and have a very similar appearance. Definitive differentiation is possible only through detailed laboratory analysis. ## Crystal Forms Argentobaumhauerite forms small, poorly developed crystals with a bladed or prismatic habit, often elongated along one axis. They usually occur as inclusions in other minerals, mainly in dolomite.
Geological environment
## Genesis It is a hydrothermal mineral, crystallizing at low temperatures. It forms in metasomatic deposits, within carbonate rocks (dolomites) that have been altered by solutions rich in sulfur, arsenic, lead, and other metals. ## Mineral Associations It most commonly co-occurs with other lead and arsenic sulfosalts, such as baumhauerite, rathite, sartorite, dufrenoysite, as well as with realgar, orpiment, and pyrite. The accompanying mineral is usually dolomite, which serves as the host rock. ## Localities The only confirmed and well-documented locality for argentobaumhauerite worldwide is the Lengenbach quarry in the Binn Valley (Binntal) in Valais canton, Switzerland. This is the type locality (*località classica*) for this mineral.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of an argentobaumhauerite specimen is primarily determined by the degree of crystal development and size, which is rare. Specimens with distinct, even if small, crystals set against a contrasting matrix, most often white dolomite, are highly valued. Association with other rare sulfosalts is also important. ## Popular Localities The only source of collector specimens is the Lengenbach quarry in Switzerland. Material from this locality is highly sought after by collectors specializing in systematic minerals and micromounts.
Care and storage
## Cleaning Argentobaumhauerite specimens are extremely delicate and rare. Cleaning should be kept to an absolute minimum. If necessary, compressed air can be used to remove dust. Avoid contact with water and any chemical agents. ## What to Avoid The mineral is sensitive to chemicals, especially acids, which can damage it. Avoid ultrasonics, steam cleaners, and sudden temperature changes. As a sulfosalt, it may be sensitive to prolonged exposure to humid air. ## Storage It is recommended to store specimens in stable conditions, in sealed, dry containers (e.g., micromount boxes), away from light and contaminants. Protect from mechanical damage, as it is a soft and brittle mineral.