Cotunnite - Encyclopedia
Class : Halides
Subclass : Chlorides
Crystal system : Orthorhombic
Chemistry : PbCl2
Rarity : Rare
Cotunnite is a rare supergene mineral from arid climate lead deposits, located in or near evaporitic basins. Like many chlorides, it is also a fumarolic mineral known in beautiful crystals, notably at Vesuvius. It was named in honor of the Italian physicist Domenico Cotugno, professor of anatomy at the University of Naples. The crystals are elongated flattened prisms of small size (2 mm maximum), sometimes united in radiated aggregates, in slags cotunnite can also form transparent pseudo-hexagonal crystals. Cotunnite also appears in crusts or massive ; it is colorless or white, sometimes yellowish or greenish.
Main photo : Cotunnite from Vesuvius, Naples, Italy © OT. Ljøstad
Cotunnite in the World
Twinning
A twin is known on {120} but only on synthetic crystals.
Fakes and treatments
No fake identified for this mineral species.
Hardness : 1.5 to 2
Density : 5.8
Fracture : Sub-conchoidal
Streak : White
TP : Transparent to translucent
RI : 2.199 to 2.260
Birefringence : 0.061
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None
Solubility : Water, hydrochloric acid, nitric acid
Magnetism : None
Radioactivity : None