Mineral - Hydroxyapophyllite-(K)
Hydroxyapophyllite-(K)
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
KCa₄(Si₈O₂₀)(OH,F) · 8H₂O
Unit Cell
a=8.98 c=15.83 Z=2
Physical Properties
Hardness
4 - 5
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {001}
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
whiteyellowgreenpinkyellow whitegreen whitepink whitecolorless
Birefringence
0.001
Luster
Vitreous,
Pearly
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
tetragonal
Point Group
ditetragonal-dipyramidal - 4/m 2/m 2/m
Space Group
P4/mnc (128)
Habit
blocky, prismatic, tabular, Cube
Formation
(1) Hydrothermal, through precipitation from late magmatic, low-temperature (usually < 200 °C) aqueous solutions in bubble spaces (amygdules) and fissures in mafic volcanic rocks.
(2) Metasomatic, in the course of low-grade metamorphism (zeolite facies) or retrograde alteration of calcium-rich rocks with the addition of fluorine and potassium ions.
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Hydroxyapophyllite-(K)
Composition
Elements
Mass
SiO₂
51.93
Al₂O₃
0.30
CaO
25.78
K₂O
4.76
Na₂O
0.09
H₂O
16.76
North Carolina (Dana 1895)
Groups and Members
Apophyllite-Group