Shigaite Mineral Data

Shigaite Mineral Data +

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General Shigaite Information

Chemical Formula:

Mn++7Al4(SO4)2(OH)22·8(H2O)

Composition:

Molecular Weight = 1,202.90 gm

Manganese 31.97 % Mn 41.28 % MnO

Aluminum 8.97 % Al 16.95 % Al₂O₃

Hydrogen 3.18 % H 28.46 % H₂O

Sulfur 5.33 % S 13.31 % SO₃

Oxygen 50.54 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Mn²⁺₇Al₄(SO₄)₂(OH)₂₂·8(H₂O)

Environment:

Found in manganosite-rhodocrosite-sonolite ore.

IMA Status:

Approved IMA 1985

Locality:

Loi mine, Shinga Prefecture, Japan. Link to MinDat.org Location Data.

Name Origin:

Named for the locality.

Synonym:

ICSD 82492

PDF 38-428

Shigaite Image

Images:

Shigaite Pyrochroite

Comments: Bronzy yellow crystals of shigaite set in a crystalline matrix of reddish black pychroite.
Location: N'Chwaning Mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Scale: 2.8 x 2.3 cm.
© John Veevaert

Images:

Shigaite

Comments: Cluster of sharp, transparent crystals of brown shigaite to 1.2 cm across.
Location: N'Chwaning mine. South Africa. Scale: Aggregate size 1.2 cm.
© John Veevaert

Images:

Shigaite

Comments: Hexagonal aggregate of orange platy shigaite crystals on a jpale pink rhodocrosite matrix.
Location: N'Chwaning mine. South Africa. Scale: Crystal size 3 mm.
© Minernet

Shigaite Crystallography

Axial Ratios:

a:c = 1:3.47708

Cell Dimensions:

a = 9.512, c = 33.074, Z = 3; V = 2,591.56 Den(Calc)= 2.31

Crystal System:

Trigonal - RhombohedralH-M Symbol ( 3) Space Group: R 3

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 10.98(1), 2.547(0.9), 5.47(0.9),

Crystal Structure:

Mouse
drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
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S - Stereo Pair on/off
H - Help Screen
I - Data Info
A - Atoms On/Off
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Help on Above

Cooper M A , Hawthorne F C , The Canadian Mineralogist , 34 (1996) p.91-97, The crystal structure of shigaite, [AlMn2(OH)6]3(SO4)2Na(H2O)6{H2O}6, a, hydrotalcite-group mineral

Physical Properties of Shigaite

Cleavage:

[0001] Perfect, [0001] Good

Color:

Light yellow, Orange.

Density:

2.32

Diaphaniety:

Transparent to Translucent

Fracture:

Flexible - Flexible fragments.

Habit:

Hexagonal - Six-sided crystal shape in cross-section or habit.

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

2 - Gypsum

Luminescence:

Non-fluorescent.

Streak:

yellow white

Optical Properties of Shigaite

Dichroism (e):

very light yellow.

Dichroism (w):

light yellow.

Gladstone-Dale:

CI meas= 0.006 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.002 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2364,KPDmeas= 0.2353,KC= 0.2367

Optical Data:

Uniaxial (-), w=1.546.

Calculated Properties of Shigaite

Electron Density:

r_electron=2.31 gm/cc
note: r_Shigaite=2.31 gm/cc.

Fermion Index

Fermion Index = 0.00064
Boson Index = 0.99936

Photoelectric:

PE_Shigaite= 8.58 barns/electron
U=PE_Shigaite x r_electron= 19.81 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Shigaite is Not Radioactive

Shigaite Classification

Dana Class:

31.1.2.1 (31)Hydrated Sulfates Containing Hydroxyl or Halogen

(31.1)where (A+ B++)m (XO4)p Zq·x(H2O), where m:p>6:1

(31.1.2)Dana Group

31.1.2.1 Shigaite Mn7Al4(SO4)2(OH)22·8(H2O) R 3 3

31.1.2.2 Nikischerite! NaFe6Al3(SO4)2(OH)18(H2O)12 R 3 3

Strunz Class:

VI/D.14-23 VI - Sulfates,Chromates,Molybdates and Tungstates

VI/D - Water-bearing sulfates with unfamiliar anions. cations of medium and very big size

VI/D.14 - Metavoltine - Slavikite series

VI/D.14-10 Metavoltine K4Na4(Fe,Zn)Fe6(SO4)12O2·20(H2O) P 3 3

VI/D.14-20 Motukoreaite Na2Mg38Al24(CO3)13(SO4)8(OH)108·56(H2O) R 3m 3 2/m

VI/D.14-22 Nikischerite! NaFe6Al3(SO4)2(OH)18(H2O)12 R 3 3

VI/D.14-23 Shigaite Mn7Al4(SO4)2(OH)22·8(H2O) R 3 3

VI/D.14-25 Wermlandite (Ca,Mg)Mg7(Al,Fe)2(SO4)2(OH)18·12(H2O) P 3c1 3 2/m

VI/D.14-30 Lannonite HCa4Mg2Al4(SO4)8F9·32(H2O) Unk Tetra

VI/D.14-40 Slavikite NaMg2Fe5(SO4)7(OH)6·33(H2O) R 3 3

Other Shigaite Information

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Dana8)

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Shigaite

Mn++7Al4(SO4)2(OH)22·8(H2O)
Dana No: 31.1.2.1 Strunz No: VI/D.14-23
Locality:

Notes: