Schorl Mineral Data

General Schorl Information

Chemical Formula:

NaFe++3Al6(BO3)3Si6O18(OH)4

Composition:

Molecular Weight = 1,053.38 gm

Sodium 2.18 % Na 2.94 % Na₂O

Aluminum 15.37 % Al 29.04 % Al₂O₃

Iron 15.91 % Fe 20.46 % FeO

Silicon 16.00 % Si 34.22 % SiO₂

Boron 3.08 % B 9.91 % B₂O₃

Hydrogen 0.38 % H 3.42 % H₂O

Oxygen 47.08 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

Environment:

Granites, diorites, gabbro pegmatites, greisens, skarns and quartz veins.

IMA Status:

Valid Species (Pre-IMA) 1524 (Dana # Changed from 61.3.1.10)

Locality:

Sonnenberg, Bodenmais and Spessart, Germany. Link to MinDat.org Location Data.

Name Origin:

Old name of unknown origin.

Name Pronunciation:

Schorl

Synonym:

ICSD 74180

PDF 43-1464

Tourmaline

Schorl Image

Images:

Schorl Albite

Comments: Several jet-black lustrous crystals of schorl perched on a white albite matrix.
Location: Shengus, Gilgit, Pakistan. Scale: 4 x 3 x 2 cm.
© Isaias Casanova / IC Minerals

Images:

Schorl

Comments: Parallel grouping of sharp, black schorl crystals showing terminations.
Location: Davib Ost, Erongo Mountains Namibia. Scale: Crystal size: 1.7 x 1.4 cm.
© Fabre Minerals

Schorl Crystallography

Axial Ratios:

a:c = 1:0.44996

Cell Dimensions:

a = 15.99, c = 7.195, Z = 3; V = 1,593.16 Den(Calc)= 3.29

Crystal System:

Trigonal - Ditrigonal Pyramidal H-M Symbol (3m) Space Group: R 3m

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

By Intensity(I/I_o): 2.576(1), 2.961(0.85), 3.99(0.85),

Forms:

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Forms: ( 0 2 1) ( 1 0 1) ( 1 2 0) ( 1 0 0) ( 1 0 1) ( 0 2 1)

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Physical Properties of Schorl

Cleavage:

{1011} Indistinct

Color:

Black, Brownish black, Greenish black, Bluish black.

Density:

3.1 - 3.2, Average = 3.15

Diaphaneity:

Opaque

Fracture:

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.

Habit:

Acicular - Occurs as needle-like crystals.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Habit:

Striated - Parallel lines on crystal surface or cleavage face.

Hardness:

7.5 - Garnet

Luminescence:

Piezoelectric.

Luster:

Vitreous (Glassy)

Streak:

brown

Optical Properties of Schorl

Dichroism (e):

light brown, buff, or light gray.

Dichroism (w):

dark brown, black, or deep gray.

Gladstone-Dale:

CI meas= 0.007 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.05 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1979,KPDmeas= 0.2067,KC= 0.2083
Ncalc = 1.65 - 1.69

Optical Data:

Uniaxial (-), e=1.633-1.64, w=1.66-1.672, bire=0.0270-0.0320.

Calculated Properties of Schorl

Electron Density:

Bulk Density (Electron Density)=3.10 gm/cc
note: Specific Gravity of Schorl =3.15 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_Schorl= 5.85 barns/electron
U=PE_Schorl x rElectron Density= 18.11 barns/cc.

Radioactivity:

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

Schorl Classification

Dana Class:

61.03e.01.10 (61)Cyclosilicate Six-Membered Rings

(61.03e)with borate groups (Sodic Tourmaline Subgroup)

(61.03e.01)Schorl Subgroup

61.03e.01.09 Dravite! NaMg3Al6(BO3)3Si6O18(OH)4 R 3m 3m

61.03e.01.10 Schorl! NaFe3Al6(BO3)3Si6O18(OH)4 R 3m 3m

61.03e.01.10a Schorl-(F)! NaFe3Al6Si6O18)(BO3)3(OH)3(F,OH) R 3m 3m

61.03e.01.11 Chromdravite! NaMg3(Cr,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

61.03e.01.12 Vanadiumdravite! NaMg3V6(Si6O18)(BO3)3(OH)4 R 3m 3m

Strunz Class:

09.CK.05 09 - SILICATES (Germanates)

09.C - Cyclosilicates

09.CK -[Si6O18]12- 6-membered single rings, with insular complex anions

09.CK.05 Chromdravite! NaMg3(Cr,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Feruvite! (Ca,Na)(Fe,Mg,Ti)3(Al,Mg,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Dravite NaMg3Al6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Buergerite! NaFe3Al6(BO3)3Si6O21F R 3m 3m

09.CK.05 Foitite! []Na<0.5(Fe,Al)3Al6Si6O18(BO3)3(OH)4 R 3m 3m

09.CK.05 Liddicoatite! Ca(Li,Al)3Al6(BO3)3Si6O18(O,OH,F)4 R 3m 3m

09.CK.05 Elbaite Na(Li,Al)3Al6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Rossmanite! []LiAl2Al6(Si6O18)(BO3)3(OH)4 R 3m 3m

09.CK.05 Olenite! NaAl3Al6(BO3)3(Si6O18)(O,OH)4 R 3m 3m

09.CK.05 Povondraite! (Na,K)(Fe,Fe)3(Fe,Mg,Al)6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Schorl NaFe3Al6(BO3)3Si6O18(OH)4 R 3m 3m

09.CK.05 Uvite (Ca,Na)(Mg,Fe)3Al5Mg(BO3)3Si6O18(OH,F)4 R 3m 3m

09.CK.05 Vanadiumdravite! NaMg3V6(Si6O18)(BO3)3(OH)4 R 3m 3m

09.CK.05 Magnesiofoitite! [](Mg2Al)Al6(Si6O18)(BO3)3(OH)4 R 3m 3m

09.CK.05 Hydroxyuvite! CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH) R 3m 3m

09.CK.05 Schorl-(F)! NaFe3Al6Si6O18)(BO3)3(OH)3(F,OH) R 3m 3m

Other Schorl Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Schorl

NaFe++3Al6(BO3)3Si6O18(OH)4
Dana No: 61.03e.01.10 Strunz No: 09.CK.05
Locality:

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