Mineral - Astrophyllite
Astrophyllite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
K₂Na(Fe²⁺,Mn²⁺)₇Ti₂[O₂|F|(OH)₄|Si₈O₂₄]
Unit Cell
a=5.36 b=11.76 c=21.08 α=86° β=90° γ=103° Z=2
Physical Properties
Hardness
3 - 3.5
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {001}, indistinct after {100}
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
brownyellowgoldbronze
Birefringence
0.050
Luster
Vitreous,
Greasy,
Pearly
Transparency
translucent,
opaque
Pleochroism
X: Rot-Orange
Y: Orange-Gelb
Z: Gelb-Grün
Geomineralogical Properties
Crystal System
triclinic
Point Group
triclinic-pinacoidal - 1
Space Group
P 1 (2)
Habit
leafy, prismatic, radial, star-shaped, tabular
Formation
Magmatic, in alkali-rich plutonites and pegmatites ; also in metamorphic gneisses
Paragenesis
Twinning
Rarity
Common
Synonyms
Astrophyllite
Composition
Elements
Mass
SiO₂
36.64
TiO₂
10.76
ZrO₂
0.66
Nb₂O₅
0.77
FeO
31.50
MnO
5.68
CaO
0.98
Na₂O
2.52
K₂O
5.13
H₂O
4.92
Greenland (Dana 1892)
Groups and Members
Astrophyllite-Supergroup
Astrophyllite-Group
Name and first discovery : Named after the ancient Greek words "astron" for "star" and "phyllon" for "leaf," due to the mineral's radial, layered morphology. First described in 1848.
Chemistry :
Synonyms : Astrofillite, Asterophyllite
Varieties :
Abbreviation : Branch
literature
Dana, J. D., & Dana, E. S. (1892). The system of mineralogy of James Dwight Dana, 1837-1868: descriptive mineralogy . J. Wiley & sons.