Potassium Calcium Silicate Aluminate
[Na9-1,Ca0-4(Si27Al9)O72]*28(H2O)
Chemical name
Potassium Calcium Silicate Aluminate
Mineral name
Stilbite
Chemical formula
[Na9-1,Ca0-4(Si27Al9)O72]*28(H2O)
Crystal system
monoclinic
Crystal Class
monoclinic-prismatic (2/m)
Space Group
C2/m
Unit cell
a [Å]:13.63
b [Å]:18.17
c [Å]:11.31
Formula units
Z=4
Twinning
common on {001} (penetration twinning)
Mohs hardness
3.5 - 4
Density [g/cm3]
2.1 - 2.2
Cleavage
perfect on {010}
Fracture / Tenacity
uneven to conchoidal
Color
colorless (usually), white, pink
Streak
white
Transparency
transparent to translucent
Optical character
biaxial (-)
Refractive Index
nα=1.484-1.500; nβ=1.492-1.507; nΥ=1.494-1.513