Schorl Mineral Data

Schorl Mineral Data +

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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 20.47 % 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)

Locality:

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

Name Origin:

Old name of unknown origin.

Synonym:

ICSD 74180

PDF 43-1464

Schorl - (61.3.1.10)

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 PyramidalH-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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Crystal Structure:

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Bloodaxe E S , Hughes J M , Dyar M D , Grew E S , Guidotti C V , American Mineralogist , 84 (1999) p.922-928, Linking structure and chemistry in the schorl-dravite series, Sample 108749

View Additional jPOWD Structure files for Schorl
[1] [2] [3] [4] [5] [6] [7] [8]

Physical Properties of Schorl

Cleavage:

[1011] Indistinct

Color:

Black, Brownish black, Greenish black, Bluish black.

Density:

3.1 - 3.2, Average = 3.15

Diaphaniety:

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= 0.144 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= 0.18 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1979,KPDmeas= 0.2067,KC= 0.2415

Optical Data:

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

Calculated Properties of Schorl

Electron Density:

r_electron=3.10 gm/cc
note: r_Schorl=3.15 gm/cc.

Fermion Index

Fermion Index = 0.01719
Boson Index = 0.98281

Photoelectric:

PE_Schorl= 5.85 barns/electron
U=PE_Schorl x r_electron= 18.11 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Schorl is Not Radioactive

Schorl Classification

Dana Class:

61.3e.1.10 (61)Cyclosilicate Six-Membered Rings

(61.3e)with borate groups (Sodic Tourmaline Subgroup)

(61.3e.1)Dana Group

61.3e.1.9 Dravite! NaMg3Al6(BO3)3Si6O18(OH)4 R 3m 3m

61.3e.1.10 Schorl ! NaFe3Al6(BO3)3Si6O18(OH)4 R 3m 3m

61.3e.1.11 Chromdravite! NaMg3(Cr,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

61.3e.1.12 Vanadiumdravite! NaMg3V6(Si6O18)(BO3)3(OH)4 R 3m 3m

Strunz Class:

VIII/E.19-50 VIII - Silicates

VIII/E - Cyklosilicates, six rings [Si6O18]12-

VIII/E.19 - Tourmaline group

VIII/E.19-05 Rossmanite! []LiAl2Al6(Si6O18)(BO3)3(OH)4 R 3m 3m

VIII/E.19-10 Elbaite Na(Li,Al)3Al6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-15 Magnesiofoitite! [](Mg2Al)Al6(Si6O18)(BO3)3(OH)4 R 3m 3m

VIII/E.19-20 Dravite NaMg3Al6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-30 Chromdravite! NaMg3(Cr,Fe)6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-35 Vanadiumdravite! NaMg3V6(Si6O18)(BO3)3(OH)4 R 3m 3m

VIII/E.19-50 Schorl NaFe3Al6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-55 Foitite! []Na<0.5(Fe,Al)3Al6Si6O18(BO3)3(OH)4 R 3m 3m

VIII/E.19-60 Olenite! NaAl3Al6(BO3)3(Si6O18)(O,OH)4 R 3m 3m

VIII/E.19-70 Buergerite! NaFe3Al6(BO3)3Si6O21F R 3m 3m

VIII/E.19-75 Povondraite! (Na,K)(Fe,Fe)3(Fe,Mg,Al)6(BO3)3Si6O18(OH)4 R 3m 3m

VIII/E.19-80 Liddicoatite! Ca(Li,Al)3Al6(BO3)3Si6O18(O,OH,F)4 R 3m 3m

VIII/E.19-90 Uvite (Ca,Na)(Mg,Fe)3Al5Mg(BO3)3Si6O18(OH,F)4 R 3m 3m

VIII/E.19-100 Feruvite! (Ca,Na)(Fe,Mg,Ti)3(Al,Mg,Fe)6(BO3)3Si6O18(OH)4 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: 61.3e.1.10 Strunz No: VIII/E.19-50
Locality:

Notes: