Mineral - Vivianite
Vivianite
Chemical Properties
Mineral Class
Phosphates
Toxicity
none
Formula
Fe²⁺Fe²⁺₂(PO₄)₂ · 8H₂O
Unit Cell
a=10.09 b=13.44 c=4.71 β=104° Z=2
Physical Properties
Hardness
1.5 - 2
Streak
whiteblueblue white
Density
Normal (2-3,5)
Cleavage
Perfect after {010}
Fracture
fibrous
Tenacity
Inelastic-flexible
Optical Properties
Color
blackgreenblueviolet
Birefringence
0.059
Luster
Vitreous,
Pearly
Transparency
translucent,
transparent
Pleochroism
Blau-Grün
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
C2/m (12)
Habit
acicular, prismatic, radial
Formation
(1) Secondarily in reducing, iron-rich environments through the reaction of dissolved iron(II) with phosphate from organic material under anoxic conditions in lacustrine sediments, peatlands, or marine shelf areas.
(2) As an oxidation product of iron phosphates in pegmatites or through the weathering of iron-bearing sulfides in the presence of phosphate-containing solutions.
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Vivianite
Composition
Elements
Mass
P₂O₅
27.17
SiO₂
0.10
FeO
44.10
H₂O
27.95
Delaware (Palache et al. 1952)
Groups and Members
Vivianite-Group