Boralsilite Mineral Data

Boralsilite Mineral Data +

General Boralsilite Information

Chemical Formula:

Al16B6Si2O27

Composition:

Molecular Weight = 1,144.71 gm

Aluminum 37.71 % Al 71.26 % Al₂O₃

Silicon 4.91 % Si 10.50 % SiO₂

Boron 5.67 % B 18.25 % B₂O₃

Oxygen 51.71 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Al₁₆B₆Si₂O₃₇

Environment:

Found in a tourmaline - quartz intergrowth in granitic pegmatite cutting granulite-facies metapelitic rocks, Structurally related to sillimanite.

IMA Status:

Approved IMA 1998 (Dana # Added)

Locality:

Stornes Peninsula, Larsemann Hills, Prydz Bay, east Antarctica. Almgjotheii in the aureole of the Rogaland intrusive complex, southwestern Norway. Link to MinDat.org Location Data.

Name Origin:

Named after its composition of (bo)ron, (al)uminum, and (sil)icon.

Synonym:

ICSD 87662

IMA1996-029

PDF 51-1451

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Boralsilite Crystallography

Axial Ratios:

a:b:c =2.6492:1:2.7052

Cell Dimensions:

a = 14.767, b = 5.574, c = 15.079, Z = 2; beta = 91.96° V = 1,240.45 Den(Calc)= 3.06

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/m

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

By Intensity(I/I_o): 5.19(1), 4.31(0.7), 5.41(0.7),

Crystal Structure:

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Peacor D R , Rouse R C , Grew E S , American Mineralogist , 84 (1999) p.1152-1161, The crystal structure of boralsilite and its relation to a family of, boroaluminosilicates, sillimanite, and andalusite

Physical Properties of Boralsilite

Cleavage:

[???] Fair, [???] Fair

Color:

White, Colorless.

Density:

3.06

Diaphaniety:

Transparent

Habit:

Aggregates - Made of numerous individual crystals or clusters.

Habit:

Fibrous - Crystals made up of fibers.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Boralsilite

Gladstone-Dale:

CI meas= -0.004 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.004 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2095,KPDmeas= 0.2095,KC= 0.2086

Optical Data:

Biaxial (+), a=1.629, b=1.64, g=1.654, bire=0.0250, 2V(Calc)=84, 2V(Meas)=81.8. Dispersion very weak, r > v.

Calculated Properties of Boralsilite

Electron Density:

r_electron=3.00 gm/cc
note: r_Boralsilite=3.06 gm/cc.

Fermion Index

Fermion Index = 0.01381
Boson Index = 0.98619

Photoelectric:

PE_Boralsilite= 1.35 barns/electron
U=PE_Boralsilite x r_electron= 4.06 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Boralsilite is Not Radioactive

Boralsilite Classification

Dana Class:

56.3.3.1 (56)Sorosilicate Si2O7 Groups and O, OH, F. and H2O

(56.3)with [Si2O7] with borate groups

(56.3.3)Dana Group

56.3.3.1 Boralsilite ! Al16B6Si2O27 C 2/m 2/m

Strunz Class:

VIII/B.31-45 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 Boralsilite Information

References:

NAME( MinRec) PHYS. PROP.(Am.Min.,Vol?83,p638-651,1998) OPTIC PROP.(MinRec)

See Also:

Links to other databases for Boralsilite :
1 -Am. Min. Crystal Structure Database 2 -Athena 3 -Google Images 4 -Google Scholar 5 -MinDAT 6 -MinMax(Deutsch) 7 -MinMax(English) 8 -Mineralienatlas (Deutsch) 9 -QUT Mineral Atlas

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Boralsilite

Al16B6Si2O27
Dana No: 56.3.3.1 Strunz No: VIII/B.31-45
Locality:

Notes: