THE MINERAL PHOSGENITE
- Chemistry: Pb2CO3Cl2, Lead Carbonate Chloride
- Class: Carbonate
- Uses: Only as mineral specimens.
Phosgenite is a relatively rare mineral and has a rare symmetry, tetragonal, for a carbonate mineral.
It has a high luster due to its lead content, just as glass crystal sparkles more when its lead content increases.
Phosgenite also fluoresces bright yellow under UV light, adding to its desirability as a collection piece.
Phosgenite forms from the oxidation of lead bearing minerals such as when galena comes in contact with carbonated and chlorinated waters.
As an interesting footnote, phosgenite has been found in the Mediterranean Sea's slag dumps of the ancient greeks.
The lead rich rocks have reacted with the sea water over time forming phosgenite crystals.
- Color is colorless, white, brown to yellow
- Luster is adamantine to greasy.
- Transparency: Crystals are transparent to translucent.
- Crystal System is tetragonal; 4 2 2
- Crystal Habits: Generally crystals are long slender prismatic to acicular with either a pinacoidal, a tetragonal trapezohedral or a pyramidal termination that tappers due to multiple secondary pyramidal faces.
Can also be stubby, tabular, massive and granular.
Large crystals (some up to half a foot long) are weakly striated lengthwise.
- Hardness is 2.+ - 3.0; a fingernail (hardness 2.5) will scratch a prism face parallel to the long axis, but not across it.
- Specific Gravity is 6.0+ (very heavy for translucent minerals)
- Cleavage is good in two directions lengthwise (prismatic), poor basal cleavage
- Fracture is conchoidal.
- Streak is white.
- Associated Minerals include cerussite, anglesite, galena and limonite.
- Other Characteristics: Usually exhibits a bright yellow fluorescence in ultraviolet light.
- Notable Occurrences include Tsumeb, Namibia; Sardinia, Italy; Tiger Mine, Arizona, Inyo Co., California and Colorado, USA; Matlock, England and Laurium, Greece.
- Best Field Indicators are fluorescence, density, variable hardness, color, crystal habit and high luster.