Mineral - Pyromorphite
Pyromorphite
Chemical Properties
Mineral Class
Phosphates
Toxicity
low
Formula
Pb₅[Cl|(PO₄)₃][
Unit Cell
a=9.99 c=7.33 Z=2
Physical Properties
Hardness
3.5 - 4
Streak
white
Density
Very Heavy (>6)
Cleavage
Fracture
conchoidal,
uneven
Tenacity
Brittle
Optical Properties
Color
browngrayorangeyellowgreen
Birefringence
0.010
Luster
Greasy,
Adamantine
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
hexagonal
Point Group
hexagonal-dipyramidal - 6/m
Space Group
P6 3 /m (176)
Habit
blocky, prismatic, pyramidal, tabular, barrel-shaped
Formation
Secondary, in the oxidation zone of lead deposits, through the reaction of Pb²⁺ derived from the weathering of primary sulfides (primarily galena) with phosphate from solutions of biogenic or sedimentary origin (e.g., apatite) under slightly acidic, oxidizing conditions.
Paragenesis
Twinning
Rarity
Common
Synonyms
Pyromorphite
Composition
Elements
Mass
P₂O₅
16.11
As₂O₅
0.13
PbO
81.33
Cl
2.71
O=Cl₂
0.61
Germany (Palache et al. 1952)
Groups and Members
Apatite-Supergroup
Apatite-Group