Mineral - Creedite
Creedite
Chemical Properties
Mineral Class
Sulphates
Toxicity
none
Formula
Ca₃[Al₂(F,OH)₁₀|SO₄]·2H₂O
Unit Cell
a=13.94 b=8.61 c=9.99 β=94° Z=4
Physical Properties
Hardness
4
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {100}
Fracture
conchoidal
Tenacity
Brittle
Optical Properties
Color
brownyellowvioletcolorless
Birefringence
0.024
Luster
Vitreous
Transparency
transparent
Pleochroism
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
C2/c (15)
Habit
prismatic
Formation
hydrothermal
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Creedite
Composition
Elements
Mass
SO₄
19.10
Al₂O₃
21.42
CaO
35.18
F
30.30
H₂O
10.72
O = F₂
17.28
USA (Palache et al. 1952)