Mineral - Annite
Annite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
KFe²⁺₃[(OH,F)₂|AlSi₃O₁₀]
Unit Cell
a=5.39 b=9.32 c=10.27 β=101° Z=2
Physical Properties
Hardness
2.5 - 3
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {001}
Fracture
uneven
Tenacity
Elastic-flexible
Optical Properties
Color
blackbrown
Birefringence
0,066
Luster
Vitreous,
Pearly
Transparency
translucent,
transparent,
opaque
Pleochroism
X: Braun
Y: Schwarz-Braun
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
C2/m (12)
Habit
leafy, blocky, coarse, granular, platelet-shaped, prismatic, tabular, barrel-shaped
Formation
Metamorphism, Igneous
Paragenesis
Twinning
Rarity
Very common
Synonyms
Annite
Composition
Elements
Mass
SiO₂
34.90
TiO₂
0.01
Al₂O₃
10.90
FeO
36.19
MnO
1.77
MgO
3.40
CaO
0.15
Na₂O
0.01
K₂O
8.10
F
2.22
Cl
0.24
H₂O
2.11
Australia (Dana 1892)
Groups and Members
Mica-Supergroup
Biotite-Group
Name and first recorded : Named after the type locality of Cape Ann, Essex County, Massachusetts, USA. First described in 1868.
Chemistry :
Synonyms :
Varieties :
Abbreviation : Ann
literature
Dana, J. D., & Dana, E. S. (1892). The system of mineralogy of James Dwight Dana, 1837-1868: descriptive mineralogy . J. Wiley & sons.