Mineral - Laumontite
Laumontite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Ca[Al₂Si₄O₁₂]·4H₂O
Unit Cell
a=14.72 b=13.08 c=7.56 β=112° Z=4
Physical Properties
Hardness
3 - 4
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {010} and {110}
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
whitebrowngrayyellow
Birefringence
0.012
Luster
Vitreous
Transparency
translucent,
transparent,
opaque
Pleochroism
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
C2/m (12)
Habit
fibrous, massive, prismatic
Formation
(1) Hydrothermal, through precipitation from low-temperature (<200°C), weakly alkaline aqueous solutions in cavities and fissures of mafic magmatites (volcanic structures).
(2) Diagenetic, through the transformation of volcaniclastic sediments or zeolite facies metamorphism under moderate pressure and low temperatures.
(3) Autigenic, as cement in sandstones through the decomposition of unstable plagioclase or volcanic glasses.
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Laumontite
Composition
Elements
Mass
SiO₂
50.70
Al₂O₃
22.53
Fe₂O₃
0.04
CaO
11.54
Na₂O
0.40
K₂O
0.30
H₂O
14.41
Deutschland (Dana 1895)
Groups and Members
Zeolite-Group
LAU-Zeolite-Group