Mineral - Dravite
Dravite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Na(Mg₃)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH)
Unit Cell
a=15.98 c=7.20 Z=3
Physical Properties
Hardness
7 - 7.5
Streak
white
Density
Normal (2-3,5)
Cleavage
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
blackbrownyellowgreen
Birefringence
Luster
Vitreous,
Greasy
Transparency
translucent,
transparent
Pleochroism
X: Gelb
Y = Z: Braun
Geomineralogical Properties
Crystal System
trigonal
Point Group
ditrigonal-pyramidal - 3m
Space Group
R3m (160)
Habit
granular, acicular, prismatic, columnar
Formation
Metamorphism, Magmatic
Paragenesis
Twinning
Rarity
Common
Synonyms
Dravite
Composition
Elements
Mass
SiO₂
36.52
TiO₂
0.17
B₂O₃
10.32
Al₂O₃
33.41
FeO
0.30
MnO
0.57
MgO
11.25
CaO
0.42
Na₂O
2.34
K₂O
0.57
F
0.12
H₂O
3.76
Slovenia (Dana 1895)
Groups and Members
Tourmaline-Group