Mineral - Arfvedsonite
Arfvedsonite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
NaNa₂(Fe²⁺)₄Fe³⁺[(OH)₂|Si₈O₂₂]
Unit Cell
a=10.00 b=18.10 c=5.33 β=104° Z=2
Physical Properties
Hardness
5.5 - 6
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {110}
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
blackgreen
Birefringence
0,014
Luster
Vitreous
Transparency
translucent,
opaque
Pleochroism
X: Blau-Grün
Y: Gelb-Braun
Z: Grau-Violett
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
C2/m (12)
Habit
fibrous, prismatic, tabular
Formation
Magmatic, mostly in alkaline plutonites and their pegmatites
Paragenesis
Twinning
Twins parallel {100}
Rarity
Common
Synonyms
Arfvedsonite
Composition
Elements
Mass
SiO₂
48.99
TiO₂
0.77
Al₂O₃
1.66
Fe₂O₃
7.52
FeO
26.56
MnO
0.94
MgO
0.45
CaO
0.93
Na₂O
6.94
K₂O
3.67
F
0.30
H₂O
1.64
Greenland (Dana 1892)
Groups and Members
Amphibole-Supergroup
Sodium-Amphibole-Group
Arfvedsonite (Arf) Amphibole-Subgroup
Name and first discovery : Named after the Swedish chemist Johan August Arfwedson (1792-1841). First described in 1823.
Synonyms : Arfwedsonite
Varieties :
Abbreviation : Arf
literature
Dana, J. D., & Dana, E. S. (1892). The system of mineralogy of James Dwight Dana, 1837-1868: descriptive mineralogy . J. Wiley & sons.