Andradite Mineral Data

General Andradite Information

Chemical Formula:

Ca3Fe+++2(SiO4)3

Composition:

Molecular Weight = 508.18 gm

Calcium 23.66 % Ca 33.11 % CaO

Iron 21.98 % Fe 28.28 % FeO

Silicon 16.58 % Si 35.47 % SiO₂

Oxygen 37.78 % O

______ ______

100.00 % 96.85 % = TOTAL OXIDE

Empirical Formula:

Ca₃Fe²⁺₂(SiO₄)₃

Environment:

Igneous and metamorphic rocks.

IMA Status:

Valid Species (Pre-IMA) 1868

Locality:

Magnet Cove, Arkansas. Link to MinDat.org Location Data.

Name Origin:

Andradite is named after the Brazilian mineralogist J. B. de Andrada e Silva (1763-1838). Demantoid is named after its adamantine luster.

Name Pronunciation:

Andradite + Pronunciation

Synonym:

Demantoid - green

ICSD 27370

Melanite - black

PDF 10-288

Topazolite - yellow

Andradite Image

Images:

Andradite Clinochlore

Comments: Transparent topazolite, the yellow variety of andradite on clinochlore.
Location: Yellow Cat Mine, New Idria District, San Benito County. California, USA. Scale: 2.7 x 2.5 cm.
© Fabre Minerals

Images:

Andradite

Comments: Andradite (var. Demantoid) Garnet.
Location: Namgar mine, Erongo Mts. Namibia. Scale: 3.5 x 3.2 cm.
© Fabre Minerals

Images:

Glagolevite Andradite

Comments: Pearly white plates of glagolevite with olive-colored andradite dodecohedrons.
Location: Zheleznyi Mine (Iron Mine), Kovdor Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia. Scale: Picture Size 12x10 mm.
© Pavel M. Kartashov

Andradite Crystallography

Cell Dimensions:

a = 12.05, Z = 8; V = 1,749.69 Den(Calc)= 3.86

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): 2.696(1), 1.6112(0.6), 3.015(0.6),

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Physical Properties of Andradite

Cleavage:

None

Color:

Black, Yellowish brown, Red, Greenish yellow, Gray.

Density:

3.7 - 4.1, Average = 3.9

Diaphaneity:

Transparent to translucent

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

Crystalline - Coarse - Occurs as well-formed coarse sized crystals.

Habit:

Euhedral Crystals - Occurs as well-formed crystals showing good external form.

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Hardness:

6.5-7 - Pyrite-Quartz

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Andradite

Gladstone-Dale:

CI meas= -0.149 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.16 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.228,KPDmeas= 0.2256,KC= 0.1965
Ncalc = 1.73 - 1.81

Optical Data:

Isotropic, n=1.87-1.89.

Calculated Properties of Andradite

Electron Density:

Bulk Density (Electron Density)=3.84 gm/cc
note: Specific Gravity of Andradite =3.90 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_Andradite= 10.08 barns/electron
U=PE_Andradite x rElectron Density= 38.70 barns/cc.

Radioactivity:

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

Andradite Classification

Dana Class:

51.04.03b.01 (51)Nesosilicate Insular SiO4 Groups Only

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

(51.04.03b)Garnet group (Ugrandite series)

51.04.03b.01 Andradite Ca3Fe2(SiO4)3 I a3d 4/m 3 2/m

51.04.03b.02 Grossular Ca3Al2(SiO4)3 I a3d 4/m 3 2/m

51.04.03b.03 Uvarovite Ca3Cr2(SiO4)3 I a3d 4/m 3 2/m

51.04.03b.04 Goldmanite Ca3(V,Al,Fe)2(SiO4)3 I a3d 4/m 3 2/m

51.04.03b.05 Yamatoite? (Mn,Ca)3(V,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 Andradite Information

References:

NAME( ODonoghue90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Mason68)

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Andradite

Ca3Fe+++2(SiO4)3
Dana No: 51.04.03b.01 Strunz No: 09.AD.25
Locality:

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