Mineral - Kyanite
Kyanite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Al₂[O|SiO₄]
Unit Cell
a=7.13 b=7.85 c=5.57 α=90° β=101° γ=106° Z=4
Physical Properties
Hardness
5.5 - 7
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {100}, distinct after {010}
Fracture
splintery
Tenacity
Brittle
Optical Properties
Color
redgreenbluevioletcolorless
Birefringence
0.016
Luster
Vitreous,
Pearly
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
triclinic
Point Group
triclinic-pinacoidal - 1
Space Group
P 1 (2)
Habit
prismatic, prismatic, tabular
Formation
(1) Regional metamorphism at medium to high pressures and relatively low temperatures (green schist facies) through the transformation of aluminum-rich pelites or metamorphic clays.
(2) Contact metamorphism within Al-rich rocks.
(3) Magmatic as an accessory in peraluminous granitoids or as a primary phase in eclogitic high-pressure rock associations.
Paragenesis
Twinning
V-shaped contact twins after {100}
Rarity
Common
Synonyms
Kyanite
Composition
Elements
Mass
SiO₂
36.68
Al₂O₃
63.28
Cr₂O₃
0.06
FeO
0.37
MgO
0.02
CaO
0.01
K₂O
0.01
Russia (Dana 1895)