Semseyite
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 4.0)
Mineral NameSemseyite
Chemical FormulaPb9Sb8S21
Mohs Hardness2.5
Crystal Systemmonoclinic
Lustermetallic
Streak Colorblackish gray
Cleavagegood on {001}
Fractureuneven
Specific Gravity6
Colorslead-gray, steel-gray, silvery-gray
Transparencyopaque
Type LocalityBrioude-Massiac (Massif Central), France
Mineral GroupSulfosalts
Usescollector
Associated Mineralsgalena, sphalerite, pyrite, quartz, siderite, barite
Rarityuncommon
Description
This specimen displays numerous small, well-formed, silvery-gray to light gray pseudo-octahedral or tabular Semseyite crystals with a metallic luster, densely covering a darker, metallic-looking matrix.
Geological Context
Semseyite is a sulfosalt mineral found in hydrothermal polymetallic veins, typically forming in low to moderate-temperature environments associated with lead-zinc-silver deposits.
