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Parallel Phosgenite Crystals

The Mineral phosgenite




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
Composition Lead chloro-carbonate
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.
Streak White
Hardness 2.5 - 3
Crystal System Tetragonal
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates
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.
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.
Complex Tests Effervesces in hydrochloric acid
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
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 2


Phosgenite AUCTIONS
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

DISTINGUISHING 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.


phosgenite PHOTOS
 
ADDITIONAL RESOURCES
 
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