Grandidierite Mineral Data

Grandidierite Mineral Data +

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:

Pegmatite.

IMA Status:

Valid Species (Pre-IMA) 1902

Locality:

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

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

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

Diaphaniety:

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

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:

r_electron=2.96 gm/cc
note: r_{Grandidierite}=3.01 gm/cc.

Fermion Index

Fermion Index = 0.01908
Boson Index = 0.98092

Photoelectric:

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

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Grandidierite is Not Radioactive

Grandidierite Classification

Dana Class:

54.1.1.1 (54)Nesosilicate Borosilicates and Some Beryllosilicates

(54.1)with (BO3)

(54.1.1)Dana Group

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

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

Strunz Class:

VIII/B.31-40 VIII - Silicates

VIII/B - Nesosubsilicates, with anions unfamiliar to tetraheders, with beryllium and boron

VIII/B.31 - Kornerupine - Harkerite series

VIII/B.31-10 Kornerupine (Mg,Fe)4(Al,Fe)6(SiO4,BO4)5(O,OH)2 C mcm 2/m 2/m 2/m

VIII/B.31-12 Prismatine! ([],Fe,Mg)(Mg,Al,Fe)5Al4Si2(Si,Al)2(B,Si,Al)(O,OH,F)22 C mcm 2/m 2/m 2/m

VIII/B.31-15 Magnesiodumortierite (Mg,Ti,[])<1(Al,Mg)2Al4Si3O18-y(OH)yBy=2-3 Pmcn 2/m 2/m 2/m

VIII/B.31-20 Dumortierite Al6.5-7(BO3)(SiO4)3(O,OH)3 Pcmn 2/m 2/m 2/m

VIII/B.31-30 Holtite Al6(Al,Ta)(BO3)[(SiO4,SbO4,AsO4)]3(O,OH)3 P nma 2/m 2/m 2/m

VIII/B.31-40 Grandidierite (Mg,Fe)Al3(BO4)(SiO4)O Pbnm 2/m 2/m 2/m

VIII/B.31-42 Ominelite! (Fe,Mg)Al3BSiO9 Pbnm 2/m 2/m 2/m

VIII/B.31-45 Boralsilite! Al16B6Si2O27 C 2/m 2/m

VIII/B.31-50 Werdingite (Mg,Fe)2Al14B4Si4O37 P1 1

VIII/B.31-60 Harkerite Ca24Mg8Al2(SiO4)8(BO3)6(CO3)10·2(H2O) R 3m 3 2/m

Other Grandidierite Information

References:

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

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Grandidierite

(Mg,Fe++)Al3(BO4)(SiO4)O
Dana No: 54.1.1.1 Strunz No: VIII/B.31-40
Locality:

Notes: