Mineral - Lazurite
Lazurite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
(Na,Ca)₈[S₂|(AlSiO₄)₆]
Unit Cell
a=9.09 Z=1
Physical Properties
Hardness
5.5
Streak
blue
Density
Normal (2-3,5)
Cleavage
Imperfect after {110}
Fracture
conchoidal
Tenacity
Brittle
Optical Properties
Color
blue
Birefringence
Luster
Vitreous
Transparency
opaque
Pleochroism
Geomineralogical Properties
Crystal System
isometric
Point Group
hextetrahedral - 4 3m
Space Group
P 4 3n (218)
Habit
dodecahedron, massive, Cube
Formation
(1) Through contact metasomatism (skarn formation) at the boundary between silicate intrusions and impure limestones or marbles under high temperatures and with the involvement of sulfur-containing fluid phases.
(2) Through high-grade metamorphism (amphibolite to granulite facies) of sulfate-rich, evaporitic carbonate sediments.
Paragenesis
Twinning
Rarity
Common
Synonyms
Lazurite, Lapis, Lapis lazuli, Lapislazuli
Composition
Elements
Mass
SiO₂
31.34
Al₂O₃
26.27
Fe₂O₃
0.27
MgO
2.47
CaO
7.97
Na₂O
15.75
K₂O
1.02
Cl
0.78
H₂O
3.87
SO₃
8.71
S
1.84
S = O,Cl₂
0.67
Afghanistan (Dana 1895)
Groups and Members
Feldspathoid-Group
Sodalite Group