Grandidierite Mineral Data

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General Grandidierite Information

Chemical Formula:

(Mg,Fe++)Al3(BO4)(SiO4)O

Composition:

Molecular Weight = 296.03 gm

Magnesium 6.16 % Mg 10.21 % MgO

Aluminum 27.34 % Al 51.67 % Al₂O₃

Iron 4.72 % Fe 6.07 % FeO

Silicon 9.49 % Si 20.30 % SiO₂

Boron 3.65 % B 11.76 % B₂O₃

Oxygen 48.64 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Mg_0.75Fe²⁺_0.25Al₃(BO₄)(SiO₄)O

Environment:

Rare accessory mineral in aluminous boron-rich rocks, thermally and high-grade regionally metamorphosed under low pressure; in pegmatites, aplites, gneisses; in xenoliths.

IMA Status:

Valid Species (Pre-IMA) 1902

Locality:

Andrahomana, southwest of Fort Dauphin, southern Madagascar. Link to MinDat.org Location Data.

Name Origin:

Named for Alfred Grandidier (1836-1912), French naturalist and explorer, an authority on Madagascar.

Name Pronunciation:

Grandidierite + Pronunciation

Synonym:

ICSD 36064

PDF 18-581

Grandidierite Image

Images:

Grandidierite

Comments: Translucent blue-green crystalline grandidierite in pegmatite.
Location: Vohibola, Madagascar. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Images:

Grandidierite Boralsilite

Comments: B&W PPL image of aggregates of boralsilite in quartz near grandidierite. Pyrite is partially replaced by oxide. Abbrev: A+B = Secondary andalusite, B = boralsilite, G = grandidierite, P = pyrite, Q = quartz. (AmMin v93:294).
Location: Pegmatites from the Larsemann Hills, East Antarctica. Scale: See Image.
© American Mineralogist

Grandidierite Crystallography

Axial Ratios:

a:b:c =0.9417:1:0.5245

Cell Dimensions:

a = 10.34, b = 10.98, c = 5.76, Z = 4; V = 653.95 Den(Calc)= 3.01

Crystal System:

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

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

By Intensity(I/I_o): 5.04(1), 5.17(1), 5.48(0.8),

Crystal Structure:

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Stephenson D A , Moore P B , Acta Crystallographica, Section B , 24 (1968) p.1518-1522, The crystal structure of grandidierite, (Mg,Fe)Al3SiBO9, Locality: Fort Dauphin, Madagascar

Physical Properties of Grandidierite

Cleavage:

{100} Good, {010} Good

Color:

Bluish green.

Density:

2.976

Diaphaneity:

Transparent to translucent

Fracture:

Brittle - Uneven - Very brittle fracture producing uneven fragments.

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

7.5 - Garnet

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Grandidierite

Gladstone-Dale:

CI meas= -0.019 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= -0.008 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2079,KPDmeas= 0.2102,KC= 0.2063
Ncalc = 1.61 - 1.62

Optical Data:

Biaxial (-), a=1.602, b=1.636, g=1.639, bire=0.0370, 2V(Calc)=32, 2V(Meas)=24-32. Dispersion strong, r < v.

Pleochroism (x):

dark bluish green.

Pleochroism (y):

colorless.

Pleochroism (z):

dark green.

Calculated Properties of Grandidierite

Electron Density:

Bulk Density (Electron Density)=2.96 gm/cc
note: Specific Gravity of Grandidierite =3.01 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_{Grandidierite}= 2.74 barns/electron
U=PE_{Grandidierite} x rElectron Density= 8.10 barns/cc.

Radioactivity:

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

Grandidierite Classification

Dana Class:

54.01.01.01 (54)Nesosilicate Borosilicates and Some Beryllosilicates

(54.01)with (BO3)

(54.01.01)Grandidierite Group

54.01.01.01 Grandidierite (Mg,Fe)Al3(BO4)(SiO4)O Pbnm 2/m 2/m 2/m

54.01.01.02 Ominelite! (Fe,Mg)Al3BSiO9 Pbnm 2/m 2/m 2/m

Strunz Class:

09.AJ.05 09 - SILICATES (Germanates)

09.A - Nesosilicates

09.AJ -Nesosilicates with BO3 triangles and/or B[4], Be[4] tetrahedra,

09.AJ.05 Grandidierite (Mg,Fe)Al3(BO4)(SiO4)O Pbnm 2/m 2/m 2/m

09.AJ.05 Ominelite! (Fe,Mg)Al3BSiO9 Pbnm 2/m 2/m 2/m

Other Grandidierite Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

See Also:

Links to other databases for Grandidierite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - Google Images
6 - Google Scholar
7 - Handbook of Mineralogy (MinSocAm)
8 - Handbook of Mineralogy (UofA)
9 - MinDAT
10 - MinMax(Deutsch)
11 - MinMax(English)
12 - Mineralienatlas (Deutsch)
13 - QUT Mineral Atlas
14 - Ruff.Info

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Translate Grandidierite Mineral Data :

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Print or Cut-and-Paste your Grandidierite Specimen Label here :

Grandidierite

(Mg,Fe++)Al3(BO4)(SiO4)O
Dana No: 54.01.01.01 Strunz No: 09.AJ.05
Locality:

Notes: