Almandine Mineral Data

Almandine Mineral Data +

General Almandine Information

Chemical Formula:

Fe++3Al2(SiO4)3

Composition:

Molecular Weight = 497.75 gm

Aluminum 10.84 % Al 20.48 % Al₂O₃

Iron 33.66 % Fe 43.30 % FeO

Silicon 16.93 % Si 36.21 % SiO₂

Oxygen 38.57 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Fe²⁺₃Al₂(SiO₄)₃

Environment:

Metamorphic and pegmatitic rocks.

IMA Status:

Valid Species (Pre-IMA) Prehistoric

Locality:

Alabanda in Asia Minor. Link to MinDat.org Location Data.

Name Origin:

Named after its locality.

Synonym:

Almandite

ICSD 28030

PDF 41-1423

Almandine Image

Images:

Almandine

Comments: Two reddish brown crystals of almandine on matrix.
Location: Fanny Gorge mine, Spruce Pine, Mitchell County, North Carolina, USA. Scale: Size Not Given.
© Lou Perloff / Photo Atlas of Minerals

Images:

Almandine Hypersthene

Comments: Dark green blocky crystals hypersthene with reddish almandine.
Location: Barton Garnet Mine, North Creek, Warren County, Adirondacks, New York, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Almandine Crystallography

Cell Dimensions:

a = 11.526, Z = 8; V = 1,531.21 Den(Calc)= 4.32

Crystal System:

Isometric - HexoctahedralH-M Symbol (4/m 3 2/m) Space Group: I a3d

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

By Intensity(I/I_o): 2.569(1), 1.54(0.5), 2.873(0.4),

Forms:

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Forms: [ 1 1 2]

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Crystal Structure:

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Novak G A , Gibbs G V , American Mineralogist , 56 (1971) p.791-825, The crystal chemistry of the silicate garnets, sample Al

View Additional jPOWD Structure files for Almandine
[1] [10] [11] [12] [2] [3] [4] [5] [6] [7] [8] [9]

Physical Properties of Almandine

Cleavage:

None

Color:

Brown, Brownish red, Red, Black, Black red.

Density:

4.09 - 4.31, Average = 4.19

Diaphaniety:

Transparent to Subtransparent to translucent

Fracture:

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.

Habit:

Granular - Generally occurs as anhedral to subhedral crystals in matrix.

Habit:

Massive - Lamellar - Distinctly foliated fine-grained forms.

Hardness:

7-8

Luminescence:

Non-fluorescent.

Luster:

Vitreous - Resinous

Streak:

white

Optical Properties of Almandine

Gladstone-Dale:

CI meas= 0.008 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.035 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1921,KPDmeas= 0.1976,KC= 0.1991

Optical Data:

Isotropic, n=1.83.

Calculated Properties of Almandine

Electron Density:

r_electron=4.08 gm/cc
note: r_Almandine=4.20 gm/cc.

Fermion Index

Fermion Index = 0.01522
Boson Index = 0.98478

Photoelectric:

PE_Almandine= 11.03 barns/electron
U=PE_Almandine x r_electron= 45.06 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Almandine is Not Radioactive

Almandine Classification

Dana Class:

51.4.3a.2 (51)Nesosilicate Insular SiO4 Groups Only

(51.4)with cations in [6] and >[6] coordination

(51.4.3a)Garnet group (Pyralspite series)

51.4.3a.1 Pyrope Mg3Al2(SiO4)3 I a3d 4/m 3 2/m

51.4.3a.2 Almandine Fe3Al2(SiO4)3 I a3d 4/m 3 2/m

51.4.3a.3 Spessartine Mn3Al2(SiO4)3 I a3d 4/m 3 2/m

51.4.3a.4 Knorringite Mg3Cr2(SiO4)3 I a3d 4/m 3 2/m

51.4.3a.5 Majorite Mg3(Fe,Al,Si)2(SiO4)3 I a3d 4/m 3 2/m

51.4.3a.6 Calderite (Mn,Ca)3(Fe,Al)2(SiO4)3 I a3d 4/m 3 2/m

Strunz Class:

VIII/A.08-20 VIII - Silicates

VIII/A - Nesosilicates with [SiO4]4-groups, cations of octahedral and cubic orientation [8+6]

VIII/A.08 - Garnet group, Pyrope - Henritermierite

VIII/A.08-10 Pyrope Mg3Al2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-20 Almandine Fe3Al2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-30 Spessartine Mn3Al2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-40 Calderite (Mn,Ca)3(Fe,Al)2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-50 Knorringite Mg3Cr2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-60 Majorite Mg3(Fe,Al,Si)2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-70 Grossular Ca3Al2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-80 Hibschite Ca3Al2(SiO4)3-x(OH)4x(x=0.2-1.5) I a3d 4/m 3 2/m

VIII/A.08-90 Katoite Ca3Al2(SiO4)3-x(OH)4xx=1.5-3 I a3d 4/m 3 2/m

VIII/A.08-100 Hydrougrandite? (Ca,Mg,Fe)3(Fe,Al)2(SiO4)3-x(OH)4x I a3d 4/m 3 2/m

VIII/A.08-110 Andradite Ca3Fe2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-120 Schorlomite Ca3(Ti,Fe,Al)2[(Si,Fe,Fe)O4]3 I a3d 4/m 3 2/m

VIII/A.08-125 Morimotoite Ca3TiFeSi3O12 I a3d 4/m 3 2/m

VIII/A.08-130 Uvarovite Ca3Cr2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-138 Yamatoite! (Mn,Ca)3(V,Al)2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-140 Goldmanite Ca3(V,Al,Fe)2(SiO4)3 I a3d 4/m 3 2/m

VIII/A.08-150 Kimzeyite Ca3(Zr,Ti)2(Si,Al,Fe)3O12 I a3d 4/m 3 2/m

VIII/A.08-160 Henritermierite Ca3(Mn,Al)2(SiO4)2(OH)4 I 4₁/acd 4/m 2/m 2/m

Other Almandine 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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Almandine

Fe++3Al2(SiO4)3
Dana No: 51.4.3a.2 Strunz No: VIII/A.08-20
Locality:

Notes: