Mineral - Wiluite
Wiluite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Ca₁₉MgAl₄(Al,Mg)₈(B, □)₄ □[Si₂O₇]₄[(SiO₄)₁₀]O(O,OH)₉
Unit Cell
a=15.75 c=11.72 Z=2
Physical Properties
Hardness
6
Streak
white
Density
Normal (2-3,5)
Cleavage
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
blackbrowngreen
Birefringence
0.004
Luster
Vitreous
Transparency
translucent,
opaque
Pleochroism
Geomineralogical Properties
Crystal System
tetragonal
Point Group
ditetragonal-dipyramidal - 4/m 2/m 2/m
Space Group
P4/nnc (126)
Habit
blocky, prismatic
Formation
Through contact metasomatism in skarns resulting from the action of boron-rich fluid phases on calc-silicate rocks, particularly during the transformation of grossular-vesuvianite associations under pneumatolytic to hydrothermal conditions.
Paragenesis
Twinning
Rarity
Very rare
Synonyms
Wiluite
Composition
Elements
Mass
SiO₂
36.11
Al₂O₃
12.03
TiO₂
0.80
MgO
6.48
FeO
1.21
Fe₂O₃
32.28
CaO
35.54
Ce₂O₃
0.18
B₂O₃
3.06
F
0.50
H₂O
0.61
O=F₂
0.24
Russia (Groat et al. 1998)
Groups and Members
Vesuvianite-Group