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.

Name Pronunciation:

Almandine + Pronunciation

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:

Hypersthene Almandine

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 - Hexoctahedral H-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),

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Physical Properties of Almandine

Cleavage:

None

Color:

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

Density:

4.09 - 4.31, Average = 4.19

Diaphaneity:

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
Ncalc = 1.81 - 1.86

Optical Data:

Isotropic, n=1.83.

Calculated Properties of Almandine

Electron Density:

Bulk Density (Electron Density)=4.08 gm/cc
note: Specific Gravity of Almandine =4.20 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_Almandine= 11.03 barns/electron
U=PE_Almandine x rElectron Density= 45.06 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Almandine is Not Radioactive

Almandine Classification

Dana Class:

51.04.03a.02 (51)Nesosilicate Insular SiO4 Groups Only

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

(51.04.03a)Garnet group (Pyralspite series)

51.04.03a.01 Pyrope Mg3Al2(SiO4)3 I a3d 4/m 3 2/m

51.04.03a.02 Almandine Fe3Al2(SiO4)3 I a3d 4/m 3 2/m

51.04.03a.03 Spessartine Mn3Al2(SiO4)3 I a3d 4/m 3 2/m

51.04.03a.04 Knorringite Mg3Cr2(SiO4)3 I a3d 4/m 3 2/m

51.04.03a.05 Majorite Mg3(Fe,Al,Si)2(SiO4)3 I a3d 4/m 3 2/m

51.04.03a.06 Calderite (Mn,Ca)3(Fe,Al)2(SiO4)3 I a3d 4/m 3 2/m

Strunz Class:

09.AD.25 09 - SILICATES (Germanates)

09.A - Nesosilicates

09.AD -Nesosilicates without additional anions;

09.AD.25 Almandine Fe3Al2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Calderite (Mn,Ca)3(Fe,Al)2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Andradite Ca3Fe2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Goldmanite Ca3(V,Al,Fe)2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Hibschite Ca3Al2(SiO4)3-x(OH)4x(x=0.2-1.5) I a3d 4/m 3 2/m

09.AD.25 Knorringite Mg3Cr2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Grossular Ca3Al2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Henritermierite Ca3(Mn,Al)2(SiO4)2(OH)4 I 4₁/acd 4/m 2/m 2/m

09.AD.25 Katoite Ca3Al2(SiO4)3-x(OH)4xx=1.5-3 I a3d 4/m 3 2/m

09.AD.25 Majorite Mg3(Fe,Al,Si)2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Kimzeyite Ca3(Zr,Ti)2(Si,Al,Fe)3O12 I a3d 4/m 3 2/m

09.AD.25 Morimotoite Ca3TiFeSi3O12 I a3d 4/m 3 2/m

09.AD.25 Pyrope Mg3Al2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Spessartine Mn3Al2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Schorlomite Ca3(Ti,Fe,Al)2[(Si,Fe,Fe)O4]3 I a3d 4/m 3 2/m

09.AD.25 Uvarovite Ca3Cr2(SiO4)3 I a3d 4/m 3 2/m

09.AD.25 Wadalite Ca6Al5Si2O16Cl3 I 43d 4 3m

09.AD.25 Holtstamite! Ca3(Al,Mn)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: 51.04.03a.02 Strunz No: 09.AD.25
Locality:

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