Mineral - Thomsonite-(Ca)
Thomsonite-(Ca)
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
NaCa₂[Al₅Si₅O₂₀] · 6H₂O
Unit Cell
a=13.09 b=13.05 c=13.23 Z=4
Physical Properties
Hardness
5 - 5.5
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {010}, distinct after {100}
Fracture
conchoidal,
uneven
Tenacity
Brittle
Optical Properties
Color
whiteyellowgreenpinkcolorless
Birefringence
0.015
Luster
Vitreous,
Pearly
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
orthorhombic
Point Group
orthorhombic-dipyramidal - 2/m 2/m 2/m
Space Group
Pnna (52)
Habit
tufty, spherical, acicular, prismatic, radial, tabular
Formation
(1) Hydrothermal, formed by precipitation from low-temperature solutions within cavities in mafic volcanic rocks (such as basalt) as a product of late crystallization or diagenesis.
(2) Autometasomatic, formed as a product of the transformation of plagioclases or feldspathoids in alkali-rich magmatic rocks.
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Thomsonite-(Ca)
Composition
Elements
Mass
SiO₂
37.17
Al₂O₃
31.93
CaO
13.98
Na₂O
4.00
K₂O
0.01
H₂O
13.35
Scotland (Dana 1895)
Groups and Members
Zeolite-Group
Thomsonite-Subgroup