Mineral - Andalusite
Andalusite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Al₂[O|SiO₄]
Unit Cell
a=7.80 b=7.90 c=5.56 Z=4
Physical Properties
Hardness
6.5 - 7.5
Streak
white
Density
Normal (2-3,5)
Cleavage
Good after {110}, poor after {100}
Fracture
conchoidal,
uneven
Tenacity
Brittle
Optical Properties
Color
browngrayredyellowgreengray brown
Birefringence
0.010
Luster
Vitreous
Transparency
translucent,
transparent,
opaque
Pleochroism
X: Rot-Orange-Braun-Pink Y: Grün-Gelb
Geomineralogical Properties
Crystal System
orthorhombic
Point Group
orthorhombic-dipyramidal - 2/m 2/m 2/m
Space Group
Pnnm (58)
Habit
blocky, granular, prismatic
Formation
Trough Contact metamorphism of clay-sediments, by regional metamorphism in schists; Igneous in granites and pegmatites
Paragenesis
Twinning
Rare after {101}
Rarity
Common
Synonyms
Andalusite
Composition
Elements
Mass
SiO₂
36.74
TiO₂
0.01
Al₂O₃
62.70
Fe₂O₃
0.36
FeO
0.05
CuO
0.02
MgO
0.03
K₂O
0.07
H₂O
0.16
Idaho (Dana 1892)
Name and first discovery : Named in 1798 by Jean-Claude Delamétherie (1743-1817) after the type locality, although this is not actually in Andalusia.
Chemistry : Polymorph with kyanite and sillimanite
Synonyms : Andalucite, Apyre, Jamesonite, Lohestite
Varieties : Chiastolite, titanium andalusite, viridin
literature
Dana, J. D., & Dana, E. S. (1892). The system of mineralogy of James Dwight Dana, 1837-1868: descriptive mineralogy . J. Wiley & sons.