What is a pseudomorph in mineralogy ?
Pseudomorph : definition
Pseudomorph is the replacement of a mineral by one or more minerals, with conservation of the original external shape of the replaced mineral.
The famous cuprite octahedra from Chessy (Rhône, France), curiously green, are o malachite pseudomorph after cuprite. Similarly, goethite cubes are pseudomorphs after goethite during surface oxidation : goethite then adopts a cubic habitus, in apparent contradiction with its orthorhombic crystal system.
Please note, this term should not be confused with epigenesis : the replacement of a fossil by a mineral (helix in lussatite, pyritized ammonites, etc...).
The famous cuprite octahedra from Chessy (Rhône, France), curiously green, are o malachite pseudomorph after cuprite. Similarly, goethite cubes are pseudomorphs after goethite during surface oxidation : goethite then adopts a cubic habitus, in apparent contradiction with its orthorhombic crystal system.
Please note, this term should not be confused with epigenesis : the replacement of a fossil by a mineral (helix in lussatite, pyritized ammonites, etc...).
Malachite pseudomorph after cuprite from Chessy, Rhône, France
Plumbogummite pseudomorph after pyromorphite from China
Copper pseudomorph after aragonite from Coro Coro Mine, Bolivia