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The Mineral phosgenite

Parallel Phosgenite Crystals

Phosgenite is very rare, and good crystals are highly cherished among experienced mineral collectors, commanding very high prices. The large crystals that were found in Monteponi in Italy are true legendary classics. Phosgenite is a difficult mineral to obtain, with no significant discoveries in recent times.

Chemical Formula

Pb₂(CO)₃Cl₂

Color

Most often amber, light orange, light brown, and yellow. Also colorless, white, light gray, and light green. May exhibit lighter and darker color zoning as well as banding in straight parallel bands.

Crystal System

Tetragonal

Properties

Streak
White

Hardness
2.5 - 3

Transparency
Transparent

Specific Gravity
6.0 - 6.3

Luster
Greasy to adamantine

Cleavage
2,1 - prismatic

Fracture
Conchoidal

Tenacity
Slightly sectile; nonbrittle

Other ID Marks
Fluoresces bright orange-yellow in shortwave ultraviolet light.

Crystal Habits

Well-developed crystals are usually long and prismatic, but may also be short and tabular and in parallel growths. Crystals are striated lengthwise, and may have pointed terminations. Besides for a few minor exceptions, large crystals have only come from the Sardinian lead mines; all other forms are usually in very small crystals or in columnar and grainy aggregates. Phosgenite crystals are very recognizable.

3D Crystal Atlas

Additional Information

Composition
Lead chloro-carbonate

In Group
Carbonates;

Striking Features
Fluorescence, high density, and characteristic crystals

Environment
As a secondary lead mineral, often found at slag localities near sea water deposits.

Rock Type
Metamorphic

Other Names

	Cromfordite
	Horn Lead

Uses

Phosgenite is of interest to collectors because of its rarity and unique crystals, and is also highly sought after by collectors who specialize on fluorescent minerals.

Noteworthy Localities

The all-time classic locality for this mineral is the Monteponi Mine, Iglesias, on the Island of Sardinia, Italy. This locality has produced large crystals with excellent form.

Two African localities have also produced good specimens, namely the Touissit Mine in Morocco and the Tsumeb Mine in Tsumeb, Namibia. Small crystals have come from Matlock, Derbyshire, England; Tarnowitz, Poland; Dundas, Tasmania, and Broken Hill, New South Wales, Australia. Phosgenite also occurs as an alteration product of the lead slags at Lavrion Greece.

Phosgenite has been found only sparingly in the U.S., particularly at the Mammoth-Saint Anthony Mine, Tiger, Pinal Co., Arizona; the Terrible Mine in Custer Co., Colorado; the Stephenson-Bennet Mine in Dona Ana Co., New Mexico; and the Silver Sprout Mine in Inyo Co., California.

Common Mineral Associations

Cerussite, Anglesite, Galena, Limonite

Distingushing Similar Minerals

Anglesite - Difficult to distinguish, though it is brittle and not sectile, and does not effervesce.
Cerussite - Different crystal habits, is brittle and not sectile.