Mineral - Fluorapophyllite-(K)
Fluorapophyllite-(K)
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
KCa₄(Si₈O₂₀)(F,OH) · 8H₂O
Unit Cell
a=8.96 c=15.80 Z=2
Physical Properties
Hardness
4.5 - 5
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {001}, imperfect after {110}
Fracture
uneven
Tenacity
Brittle
Optical Properties
Color
whitegreenblueturquoiseblue greencolorless
Birefringence
0.002
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, dipyramidal, prismatic, spear-shaped, tabular
Formation
Secondary, hydrothermal in volcanic rocks such as basalts; rarely in plutonic and metamorphic rocks
Paragenesis
Twinning
Rarity
Common
Synonyms
Fluorapophyllite-(K)
Composition
Elements
Mass
SiO₂
51.98
Al₂O₃
0.36
CaO
25.10
K₂O
4.45
Na₂O
0.61
F
2.20
H₂O
16.25
O=F₂
0.92
Michigan (Dana 1895)
Groups and Members
Apophyllite-Group