PHOSGENITE

    Class : Carbonates, nitrates, borates
    Subclass : Anhydrous carbonates
    Crystal system : Tetragonal
    Chemistry : Pb2CO3Cl2
    Rarity : Uncommon

Phosgenite is a relatively rare secondary mineral from lead deposits located in saline environments (seaside or desert evaporitic basins). It is found there associated with other secondary lead minerals such as cerussite and anglesite. It can also be present in industrial slag in the marine environment. Its name comes from the term “phosgene” which designates an extremely toxic gas : COCl2 (carbonyl dichloride). Phosgenite crystallizes in short to elongated [001] prisms with a square section, often tabular, ending in a flat face (001) or a pyramid. It is transparent to translucent and has an adamantine luster. It is yellowish white to yellowish brown, sometimes black due to galena inclusions. Soluble in acids with effevescence, it exhibits weak yellow fluorescence under long UV. It is a very accessory lead ore.

Main photo : Phosgenite from Monteponi Mine, Sardinia, Italy © Robert Lavinsky

Phosgenite from Monteponi Mine, Sardinia, Italy © Allan Young
Phosgenite from Touissit, Morocco © Orso Martinelli
Phosgenite from the Menez-Plom slag, Côtes-d’Armor, France © Jean-Paul Berthe
Phosgenite from the Laurion slag, Greece © Nazareno La Manna

Phosgenite in the World

Phosgenite was abundant in the Monteponi lead mine (Sardinia, Italy) in magnificent crystals reaching 15 cm and several kilos, these are the most beautiful specimens known, usually hidden in galena dissolution cavities. The neighboring mines of Montevecchio and Gibbas also provided splendid crystals but of smaller sizes. Very good crystals are also known in Sidi Amor Ben Salem (Tunisia) where they are reddish in color, in Touissit (Morocco) and in Tsumeb (Namibia). The Polish mine at Tarnowitz was known for its large masses and crystals frequently replaced by cerussite (pseudomorph). It is finally known in the Laurion slag (Greece).

Phosgenite in France

In France, phosgenite is reported in Farges (Corrèze) and Cap Garonne (Var), as well as in the slag of Poullaouen (Finistère) and Menez-Plom (Côtes-d'Armor).

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 2 to 3
Density : 6.12 to 6.15
Fracture : Conchoidal
Streak : White

TP : Translucent to transparent
RI : 2.118 to 2.145
Birefringence : 0.027
Optical character : Uniaxial +
Pleochroism : Low
Fluorescence : Yellow

Solubility : Nitric acid

Magnetism : NoneRadioactivity : None