Sekaninaite Mineral Data

Sekaninaite Mineral Data +

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General Sekaninaite Information

Chemical Formula:

(Fe++,Mg)2Al4Si5O18

Composition:

Molecular Weight = 632.27 gm

Magnesium 1.92 % Mg 3.19 % MgO

Aluminum 17.07 % Al 32.25 % Al₂O₃

Iron 13.25 % Fe 17.04 % FeO

Silicon 22.21 % Si 47.52 % SiO₂

Oxygen 45.55 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Fe²⁺_1.5Mg_0.5Al₄Si₅O₁₈

Environment:

Pegmatitic rocks.

IMA Status:

Approved IMA 1975

Locality:

Kolni Bory, Czechoslovakia. Link to MinDat.org Location Data.

Name Origin:

Named after the Czechoslovakian mineralogist, J. Sekanina (1901-1986).

Synonym:

ICSD 100490

PDF 31-616

Sekaninaite Image

Images:

Sekaninaite

Comments: Black-green crystalline sekaninaite cleavage with dark purple colored fracture surface.
Location: Rozna, Moravia, Jihomoravsky, Czech Republic. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Sekaninaite Crystallography

Axial Ratios:

a:b:c =1.7488:1:0.9461

Cell Dimensions:

a = 17.186, b = 9.827, c = 9.298, Z = 4; V = 1,570.31 Den(Calc)= 2.67

Crystal System:

Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: C ccm

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

By Intensity(I/I_o): 3.376(1), 3.386(1), 8.583(1),

Crystal Structure:

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Hochella M F , Brown G E , Ross F K , Gibbs G V , American Mineralogist , 64 (1979) p.337-351, High-temperature crystal chemistry of hydrous Mg- and Fe-cordierite, Dolni Bory, T = 24 C

View Additional jPOWD Structure files for Sekaninaite
[1]

Physical Properties of Sekaninaite

Cleavage:

[100] Good

Color:

Blue, Blue violet, Violet blue, Gray blue.

Density:

2.77

Diaphaniety:

Transparent to translucent

Fracture:

Brittle - Uneven - Very brittle fracture producing uneven fragments.

Habit:

Crystalline - Fine - Occurs as well-formed fine sized crystals.

Hardness:

7.5 - Garnet

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Sekaninaite

Gladstone-Dale:

CI meas= -0.008 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.046 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2134,KPDmeas= 0.2057,KC= 0.204

Optical Data:

Biaxial (-), a=1.561, b=1.572, g=1.576, bire=0.0150, 2V(Calc)=60, 2V(Meas)=66.

Calculated Properties of Sekaninaite

Electron Density:

r_electron=2.73 gm/cc
note: r_Sekaninaite=2.77 gm/cc.

Fermion Index

Fermion Index = 0.01532
Boson Index = 0.98468

Photoelectric:

PE_Sekaninaite= 5.32 barns/electron
U=PE_Sekaninaite x r_electron= 14.48 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Sekaninaite is Not Radioactive

Sekaninaite Classification

Dana Class:

61.2.1.2 (61)Cyclosilicate Six-Membered Rings

(61.2)with Al substituted rings

(61.2.1)Cordierite group

61.2.1.1 Cordierite Mg2Al4Si5O18 C ccm 2/m 2/m 2/m

61.2.1.2 Sekaninaite (Fe,Mg)2Al4Si5O18 C ccm 2/m 2/m 2/m

Strunz Class:

VIII/E.12-50 VIII - Silicates

VIII/E - Cyklosilicates, six rings [Si6O18]12-

VIII/E.12 - Beryl series

VIII/E.12-10 Beryl Be3Al2Si6O18 P 6/mmc 6/m 2/m 2/m

VIII/E.12-20 Bazzite Be3(Sc,Al)2Si6O18 P 6/mcc 6/m 2/m 2/m

VIII/E.12-25 Stoppaniite! (Fe,Al,Mg)4(Na,[])2[Be6Si12O36]·2(H2O) P 6/mmc 6/m 2/m 2/m

VIII/E.12-30 Indialite Mg2Al4Si5O18 P 6/mcc 6/m 2/m 2/m

VIII/E.12-40 Cordierite Mg2Al4Si5O18 C ccm 2/m 2/m 2/m

VIII/E.12-50 Sekaninaite (Fe,Mg)2Al4Si5O18 C ccm 2/m 2/m 2/m

Other Sekaninaite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

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Sekaninaite

(Fe++,Mg)2Al4Si5O18
Dana No: 61.2.1.2 Strunz No: VIII/E.12-50
Locality:

Notes: