Mineral - Stellerite
Stellerite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Ca₄(Si₂₈Al₈)O₇₂ · 28H₂O
Unit Cell
a=13.60 b=18.22 c=17.86 Z=8
Physical Properties
Hardness
4.5
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {010}
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
whitebrownorangegreencolorless
Birefringence
0.013
Luster
Pearly
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
orthorhombic
Point Group
orthorhombic-dipyramidal - 2/m 2/m 2/m
Space Group
Fmmm (69)
Habit
sheaf-shaped, spherical, radial, tabular, grape-shaped
Formation
(1) Hydrothermally in cavities within mafic volcanic rocks, as a late-stage deposit from low-temperature, water-rich solutions under zeolite-forming conditions.
(2) Metasomatically in skarns or along fault zones through the alteration of calcium-rich silicates under low pressure and moderate temperatures.
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Stellerite
Composition
Elements
Mass
SiO₂
59.15
Al₂O₃
14.21
Fe₂O₃
0.17
MnO
0.01
MgO
0.04
CaO
7.45
SrO
0.05
BaO
0.02
Na₂O
0.19
K₂O
0.23
H₂O
17.79
Italy (Galli & Passaglia 1973)
Groups and Members
Zeolite-Group
Stilbite-Subgroup