Mineral - Agrellite
Agrellite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
NaCa₂Si₄O₁₀F
Unit Cell
a=9.22 b=8.52 c=7.98 α=55° β=62° γ=69° Z=2
Physical Properties
Hardness
5.5
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {110} and {1 1 0}, poor after {010}
Fracture
Tenacity
Brittle
Optical Properties
Color
graygreen
Birefringence
0.014
Luster
Vitreous,
Pearly
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
triclinic
Point Group
triclinic-pinacoidal - 1
Space Group
P 1 (2)
Habit
prismatic
Formation
Formed by late-stage magmatic crystallization or metasomatic processes in peralkaline pegmatites under conditions of high fluorine activity
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Agrellite
Composition
Elements
Mass
SiO₂
57.79
TiO₂
0.01
ZrO₂
0.18
Al₂O₃
1.32
REE
2.57
Fe₂O₃
0.11
MnO
0.25
MgO
0.02
CaO
25.70
SrO
0.16
BaO
0.06
Na₂O
7.90
K₂O
0.22
F
4.45
H₂O
0.40
Canada (Gittins et al. 1976)
Name and first discovery : Named after the British petrologist and mineralogist Stuart Olaf Agrell (1913-1996), famous for his work in the Apollo space program. Discovered in Canada in 1973.
Chemistry :
Synonyms :
Varieties :
Abbreviation : Are
literature
Gittins, J., Brown, M.G., & Sturman, D. (1976). Agrellite, a new rock-forming mineral in regionally metamorphosed agpaitic alkalic rocks. The Canadian Mineralogist , 14 (2), 120-126.