Povondraite Mineral Data

Povondraite Mineral Data +

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General Povondraite Information

Chemical Formula:

(Na,K)(Fe+++,Fe++)3(Fe,Mg,Al)6(BO3)3Si6O18(OH)4

Composition:

Molecular Weight = 1,156.50 gm

Potassium 0.85 % K 1.02 % K₂O

Sodium 1.49 % Na 2.01 % Na₂O

Magnesium 3.78 % Mg 6.27 % MgO

Aluminum 1.40 % Al 2.64 % Al₂O₃

Iron 31.87 % Fe 27.02 % FeO / 15.53 % Fe₂O₃

Silicon 14.57 % Si 31.17 % SiO₂

Boron 2.80 % B 9.03 % B₂O₃

Hydrogen 0.35 % H 3.12 % H₂O

Oxygen 42.89 % O

______ ______

100.00 % 97.82 % = TOTAL OXIDE

Empirical Formula:

Na_0.75K_0.25Fe³⁺_2.25Fe²⁺_0.75Fe²⁺_3.6Mg_1.8Al_0.6(BO₃)₃(Si₆O₁₈)(OH)₄

Environment:

Found in hydrothermally altered basalt clasts in a metamorphosed evaporite deposit.

IMA Status:

Approved IMA 1993 (Dana # Changed)

Locality:

Cristalmuya gorge, near San Francisco asbestos mine, Chapare Province, Cochabamba Department, Bolivia. Link to MinDat.org Location Data.

Name Origin:

Named for Pavel Povandra (1924-), mineralogits, Charles University, Prague, Czech Repubic.

Synonym:

Ferridravite

ICSD 72941

IMA1978-075

PDF 33-1261

Povondraite - (61.3.1.6)

Tourmaline

Povondraite Image

Images:

Povondraite

Comments: Deep greenish black povondraite crystals.
Location: Malacacheta, Minas Gerais, Brazil. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Povondraite Crystallography

Axial Ratios:

a:c = 1:0.4599

Cell Dimensions:

a = 16.186, c = 7.444, Z = 3; V = 1,688.95 Den(Calc)= 3.41

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): 2.63(1), 4.05(0.9), 6.63(0.9),

Crystal Structure:

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drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
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H - Help Screen
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A - Atoms On/Off
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Help on Above

Grice J D , Ercit T S , Hawthorne F C , American Mineralogist , 78 (1993) p.433-436, Povondraite, a redefinition of the tourmaline ferridravite, Note: Atomic parameters updated by Grice on 11/20/2001.

Physical Properties of Povondraite

Cleavage:

None

Color:

Black.

Density:

3.26

Diaphaniety:

Translucent

Habit:

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

Habit:

Striated - Parallel lines on crystal surface or cleavage face.

Hardness:

7 - Quartz

Luster:

Resinous

Streak:

brown

Optical Properties of Povondraite

Dichroism (e):

light brown or light brown.

Dichroism (w):

brown or opaque.

Optical Data:

Uniaxial (-), e=1.751, w=1.82, bire=0.0690.

Calculated Properties of Povondraite

Electron Density:

r_electron=3.33 gm/cc
note: r_Povondraite=3.41 gm/cc.

Fermion Index

Fermion Index = 0.02313
Boson Index = 0.97687

Photoelectric:

PE_Povondraite= 10.33 barns/electron
U=PE_Povondraite x r_electron= 34.43 barns/cc.

Radioactivity:

GRapi = 11.91 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Povondraite - barely detectable

Povondraite Classification

Dana Class:

61.3c.1.6 (61)Cyclosilicate Six-Membered Rings

(61.3c)with borate groups (Ferric Tourmaline Subgroup)

(61.3c.1)Dana Group

61.3c.1.5 Buergerite! NaFe3Al6(BO3)3Si6O21F R 3m 3m

61.3c.1.6 Povondraite ! (Na,K)(Fe,Fe)3(Fe,Mg,Al)6(BO3)3Si6O18(OH)4 R 3m 3m

Strunz Class:

VIII/E.19-75 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 Povondraite Information

References:

NAME( Dana8) PHYS. PROP.(Am.Min.,Vol.78,p433-436,1993) OPTIC PROP.(Am.Min.,Vol.78,p433-436,1993)

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Povondraite

(Na,K)(Fe+++,Fe++)3(Fe,Mg,Al)6(BO3)3Si6O18(OH)4
Dana No: 61.3c.1.6 Strunz No: VIII/E.19-75
Locality:

Notes: