Mineral - Mimetite
Mimetite
Chemical Properties
Mineral Class
Arsenates
Toxicity
low
Formula
Pb₅[Cl|(AsO₄)₃]
Unit Cell
a=10.25 c=7.45 Z=2
Physical Properties
Hardness
3.5 - 4
Streak
white
Density
Very Heavy (>6)
Cleavage
Fracture
conchoidal,
uneven
Tenacity
Brittle
Optical Properties
Color
brownorangeyellowgreencolorless
Birefringence
0.019
Luster
Greasy,
Adamantine,
Resinous
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
hexagonal
Point Group
hexagonal-dipyramidal - 6/m
Space Group
P6 3 /m (176)
Habit
spherical, acicular, prismatic, pyramidal, radial, tabular, barrel-shaped
Formation
Secondarily, through the oxidation of lead-bearing sulfide deposits (particularly galena) in the presence of arsenate-bearing solutions under arid to semi-arid conditions in the oxidation zone
Paragenesis
Twinning
Rarity
Common
Synonyms
Mimetite
Composition
Elements
Mass
P₂O₅
0.14
As₂O₅
23.17
PbO
74.58
Cl
2.39
O=Cl₂
0.54
Pennsylvania (Palache et al. 1952)
Groups and Members
Apatite-Supergroup
Apatite-Group