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Långbanite

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Formula:
(Mn
2+
 
,Ca)
 
4
(Mn
3+
 
,Fe
3+
 
)
 
9
Sb
5+
 
(SiO
 
4
)
 
2
O
 
16
System:TrigonalColour:black
Hardness:
Name:
After the type locality: Långban, Sweden.
This page provides mineralogical data about Långbanite.

Classification of Långbanite

IMA status:Approved 1971
Strunz 8th edition ID:8/B.09-17
Nickel-Strunz 10th (pending) edition ID:9.AG.10

9 : SILICATES (Germanates)
A : Nesosilicates
G : Nesosilicates with additional anions; cations in > [6] +- [6] coordination
Dana 8th edition ID:44.3.4.1

44 : ANTIMONATES
3 : Miscellaneous
Hey's CIM Ref.:17.7.19

17 : Silicates Containing other Anions
7 : Silicates with vanadate, arsenate or antimonate
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Type Occurrence of Långbanite

Type Locality:Långban, Filipstad, Värmland, Sweden
General Appearance of Type Material:Short to long black prisms with vertical striations.
Geological Setting of type material:In crystalline limestones and manganese-rich skarns in metamorphosed manganese deposits.

Physical Properties of Långbanite

Lustre:Sub-Metallic
Diaphaneity (Transparency):Opaque
Colour:black
Streak:brown
Hardness (Mohs):
Hardness Data:Measured
Tenacity:Brittle
Cleavage:Distinct/Good
{001} good.
Fracture:Conchoidal
Density (measured):4.9 g/cm3

Crystallography of Långbanite

Crystal System:Trigonal
Class (H-M):3m - Ditrigonal Pyramidal
Space Group:P3m1
Cell Parameters:a = 11.563(2) Å, b = 11.563Å, c = 11.100(2) Å
α = 90°, β = 90°, γ = 120°
Ratio:a:b:c = 1 : 1 : 0.96
Unit Cell Volume:V 1,285.27 ų (Calculated from Unit Cell)
Morphology:Complex prismatic crystals to 1 cm.
Comment:Also reported as monoclinic, C2/m, a = 11.561(5) Å, b = 20.05(1) Å, c = 11.075(9) Å, β = 90.03(5)o by Guiseppetti et al. (1991)
X-Ray Powder Diffraction:
d-spacingIntensity
2.55 (100)
2.745 (90)
2.80 (80)
1.54 (80)
1.67 (70)
1.43 (50)
1.99 (40)

Optical Data of Långbanite

Type:Uniaxial (-)
RI values: nω = 2.360 nε = 2.310
Maximum Birefringence:δ = 0.050

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Very High
Comments:Refractive indices recorded for Li light.

Chemical Properties of Långbanite

Formula:
(Mn
2+
 
,Ca)
 
4
(Mn
3+
 
,Fe
3+
 
)
 
9
Sb
5+
 
(SiO
 
4
)
 
2
O
 
16
Essential elements:Mn, O, Sb, Si
All elements listed in formula:Ca, Fe, Mn, O, Sb, Si
Analytical Data:Average of 8 analyses reported as Analysis 2 in handbook of Mineralogy.
SiO2 (9.14)
Fe2O3 (8.56)
Mn2O3 (44.21)
Y2O3 (0.06)
Sb2O5 (14.36)
MnO (21.56)
CaO (1.11)
TOTAL (99.40)
Empirical Formula:
(Mn
2+
3.73
Ca
 
0.26
Y
 
0.01
)
 
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