Cumengeite
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NameCumengeite
Chemical FormulaPb21Cu20Cl42(OH)40
Mohs Hardness2.5
Crystal Systemtetragonal
Lustervitreous
Streak Colorpale blue
Cleavageperfect on {001}
Fractureconchoidal
Specific Gravity4.75
Colorsdeep blue, azure blue, indigo blue
Transparencytransparent
Type LocalityAmelia Mine, Santa Rosalía (El Boleo), Boleo District, Municipio de Mulegé, Baja California Sur, Mexico
Mineral GroupHalides
Usescollector, scientific research
Associated Mineralsboleite, pseudoboleite, atacamite, gypsum, anglesite, cerussite
Rarityrare
Description
This specimen features sharp, deep azure-blue tetragonal dipyramidal crystals, often twinned, forming attractive clusters. The crystals exhibit a distinct metallic-blue sheen.
Geological Context
Cumengeite is a rare secondary mineral found in the oxidized zone of lead-copper deposits, typically forming under arid conditions. It is often associated with other complex lead-copper halides.
