Mineral - Serandite
Serandite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
NaMn²⁺₂Si₃O₈(OH)
Unit Cell
a=7.68 b=6.89 c=6.75 α=91° β=94° γ=103° Z=2
Physical Properties
Hardness
5 - 5.5
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfect after {001} and {100}
Fracture
splintery,
uneven
Tenacity
Brittle
Optical Properties
Color
brownredorangepink
Birefringence
0.035
Luster
Vitreous,
Greasy
Transparency
translucent,
transparent,
opaque
Pleochroism
Geomineralogical Properties
Crystal System
triclinic
Point Group
triclinic-pinacoidal - 1
Space Group
P 1 (2)
Habit
blocky, acicular, prismatic
Formation
(1) Primarily magmatic, formed in late-stage, agpaitic alkaline pegmatites and syenites through crystallization from highly differentiated, sodium- and manganese-rich silicate melts.
(2) Hydrothermal, formed in fractures and druses through precipitation from residual solutions at moderate temperatures
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Serandite
Composition
Elements
Mass
SiO₂
48.72
Al₂O₃
0.29
Fe₂O₃
0.03
FeO
1.33
MnO
28.99
MgO
0.06
CaO
10.42
Na₂O
7.38
K₂O
0.26
H₂O
2.78
Guinea (Lacroix 1931)
Groups and Members
Wollastonite-Group