Mineral - Lazulite
Lazulite
Chemical Properties
Mineral Class
Phosphates
Toxicity
none
Formula
MgAl₂(PO₄)₂(OH)₂
Unit Cell
a=7.14 b=7.28 c=7.23 β=121° Z=5
Physical Properties
Hardness
5.5 - 6
Streak
white
Density
Normal (2-3,5)
Cleavage
Indistinct after {101} and {110}
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
greenblue
Birefringence
0.037
Luster
Vitreous
Transparency
translucent,
transparent
Pleochroism
Blautöne
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
P2 1 /c (14)
Habit
dipyramidal, granular, prismatic
Formation
(1) Primarily under hydrothermal conditions in high-aluminum, often phosphate-bearing quartz veins and pegmatites under moderate temperatures and pressures.
(2) Metamorphic in quartz-rich rocks (metaquartzites) through the conversion of aluminum precursors under conditions of green schist to amphibolite facies.
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Lazulite
Composition
Elements
Mass
P₂O₅
45.79
TiO₂
0.20
Al₂O₃
32.49
Fe₂O₃
0.60
FeO
3.95
MgO
10.38
CaO
0.06
H₂O
6.48
Georgia (Palache et al. 1952)
Groups and Members
Lazulite-Group