Montpelvouxite
Chemical formula: Ag¹⁺Pb²⁺₁₆Sb³⁺₂₇As³⁺₁₈S²⁻₈₄
Montpelvouxite is an extremely rare lead-silver antimony-arsenic sulfosalt, forming tiny, metallic grains.
Properties
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Triclinic
Diagnostic features
## Identification Identification of Montpelvouxite is possible only through advanced laboratory techniques, such as chemical composition analysis using an electron microprobe (EDS/WDS) and X-ray diffraction. Field and collector identification is impossible. ## Distinguishing from Similar Minerals Under the microscope, it can be confused with other similar lead sulfosalts, such as boulangerite, jamesonite, or zinkenite. Definitive differentiation requires chemical analysis, which will reveal the presence of silver, antimony, and arsenic in specific proportions, characteristic of Montpelvouxite. ## Crystal Forms This mineral occurs exclusively as anhedral, irregular grains intergrown with other minerals. No well-formed crystals have been observed.
Geological environment
## Genesis Montpelvouxite forms under hydrothermal conditions. It was found in quartz veins cutting amphibolite rocks. Its formation is associated with crystallization from solutions rich in sulfur, lead, antimony, arsenic, and silver. ## Mineral Associations This mineral co-occurs directly with quartz, in which it forms inclusions. Other sulfosalts identified in its surroundings include boulangerite, bournonite, dadsonite, owyheeite, semseyite, tetrahedrite, tintinaite, as well as pyrite and chalcopyrite. ## Localities The only confirmed occurrence (type locality) of Montpelvouxite in the world is the Mont Pelvoux mine in the commune of Vallouise, in the Hautes-Alpes department, Provence-Alpes-Côte d'Azur region, France.
Rarity
Extremely rare
For collectors
## Quality Criteria From a collector's perspective, the value of a Montpelvouxite specimen depends solely on the confirmation of its presence through scientific analysis. Since the mineral is invisible to the naked eye, specimens are valued as representatives of an extremely rare species from its type and only known locality. The visual appeal of the host rock (quartz) is secondary. ## Popular Localities The Mont Pelvoux mine in France is the only source of specimens. Material from this locality is extremely difficult to acquire and appears on the collector's market sporadically, usually circulating among specialized collectors and scientific institutions.
Care and storage
## Cleaning Due to its microscopic size and occurrence as inclusions in quartz, individual Montpelvouxite grains are not subject to cleaning. The host specimen (quartz) can be cleaned using standard methods, e.g., distilled water and a soft brush. ## What to Avoid Avoid contact with aggressive chemicals that could damage both the mineral itself and the host rock. Sudden temperature changes can cause cracks in the quartz. ## Storage Specimens containing Montpelvouxite should be stored in stable conditions, away from dust and moisture. It is best to keep them in sealed collector's boxes, with an accurate label indicating the presence of this rare mineral.