Obertiite Mineral Data

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General Obertiite Information

Chemical Formula:

NaNa2(Mg3Fe+++Ti)Si8O22(O,F,OH)2

Composition:

Molecular Weight = 855.28 gm

Sodium 8.06 % Na 10.87 % Na₂O

Magnesium 8.53 % Mg 14.14 % MgO

Titanium 5.60 % Ti 9.34 % TiO₂

Iron 6.53 % Fe 9.34 % Fe₂O₃

Silicon 26.27 % Si 56.20 % SiO₂

Hydrogen 0.03 % H 0.26 % H₂O

Oxygen 44.43 % O

Fluorine 0.56 % F 0.56 % F

- % F -0.23 % -O=F₂

______ ______

100.00 % 100.47 % = TOTAL OXIDE

Empirical Formula:

Na₃Mg₃Fe³⁺Ti(Si₈O₂₂)O_1.5F_0.25(OH)_0.25

Environment:

In cavities with basaltic flows. A member of the anhydrous amphibole group.

IMA Status:

Approved IMA 1998 (Dana # Added)

Locality:

The Bellerberg quarry, Laacher See district, Eifel region, Germany. Link to MinDat.org Location Data.

Name Origin:

Named for Dr. Roberta Oberti (1951-), Pavia, Italy, for her contributions to the understanding of the crystal chemistry of the amphibole group.

Synonym:

Ferric-nyboite

IMA1998-046

Obertiite Image

Images:

Obertiite

Comments: Pinkish grains of obertiite in matrix.
Location: Bellerberg Mt., Eifel District, Rheinland-Phalz, Germany. Scale: Specimen Size 7x6 mm.
© Sergey Vasiliev / Systematic Mineralogy

Obertiite Crystallography

Axial Ratios:

a:b:c =0.5455:1:0.2953

Cell Dimensions:

a = 9.776, b = 17.919, c = 5.292, Z = 2; beta = 104.05° V = 899.30 Den(Calc)= 3.16

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): 8.414(1)(110), 2.705(0.7)(331,151), 3.39(0.6)(131),2.531(0.5)(202), 3.117(0.5)(310), 4.467(0.5)(040),

Crystal Structure:

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Hawthorne F C , Cooper M A , Grice J D , Ottolini L , American Mineralogist , 85 (2000) p.236-241, A new anhydrous amphibole from the Eifel region, Germany:, Description and crystal structure of obertiite, NaNa2(Mg3FeTi)Si8O22O2, Note: M1A and M1 are interchanged in the bond length table

Physical Properties of Obertiite

Cleavage:

{110} Perfect, {110} Perfect

Color:

Pale pink.

Diaphaneity:

Transparent to Translucent

Fracture:

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

Habit:

Aggregates - Made of numerous individual crystals or clusters.

Habit:

Bladed - Aggregates of thin lath-like crystals (e.g. kyanite).

Hardness:

5 - Apatite

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Obertiite

Gladstone-Dale:

CI calc= 0.108 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2078,KC= 0.2331
Ncalc = 1.74

Optical Data:

Biaxial (-), a=1.643, b=1.657, g=1.67, bire=0.0270, 2V(Calc)=86, 2V(Meas)=81. Dispersion dispersion not observed.

Calculated Properties of Obertiite

Electron Density:

Bulk Density (Electron Density)=3.11 gm/cc
note: Specific Gravity of Obertiite =3.16 gm/cc.

Fermion Index:

Fermion Index = 0.02
Boson Index = 0.98

Photoelectric:

PE_Obertiite= 4.17 barns/electron
U=PE_Obertiite x rElectron Density= 12.98 barns/cc.

Radioactivity:

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

Obertiite Classification

Dana Class:

66.01.03c.16 (66)Inosilicate Double-Width Unbranched Chains, W=2

(66.01)with P=2 amphibole configuration

(66.01.03c)Group 4, the sodic amphiboles

66.01.03c.01 Glaucophane []Na2(Mg3Al2)Si8O22(OH)2 C 2/m 2/m

66.01.03c.02 Ferroglaucophane []Na2(Fe3Al2)Si8O22(OH)2 C 2/m 2/m

66.01.03c.03 Crossite? Na2(Mg,Fe)3(Al,Fe)2Si8O22(OH)2 C 2/m 2/m

66.01.03c.04 Magnesioriebeckite []Na2[(Mg,Fe)3Fe2]Si8O22(OH)2 C 2/m 2/m

66.01.03c.05 Riebeckite []Na2(Fe3Fe2)Si8O22(OH)2 C 2/m 2/m

66.01.03c.06 Eckermannite NaNa2(Mg4Al)Si8O22(OH)2 C 2/m 2/m

66.01.03c.07 Ferro-eckermannite NaNa2(Fe4Al)Si8O22(OH)2 C 2/m 2/m

66.01.03c.08 Magnesio-arfvedsonite NaNa2(Mg4Fe)Si8O22(OH)2 C 2/m 2/m

66.01.03c.09 Arfvedsonite NaNa2(Fe4Fe)Si8O22(OH)2 C 2/m 2/m

66.01.03c.09a Fluoro-magnesio-arfvedsonite! NaNa2(Mg,Fe)4Fe[Si8O22](F,OH)2 C 2/m 2/m

66.01.03c.09b Potassicarfvedsonite! KNa2Fe4FeSi8O22(OH)2 C 2/m 2/m

66.01.03c.10 Kozulite NaNa2Mn4(Fe,Al)Si8O22(OH)2 C 2/m 2/m

66.01.03c.11 Nyboite NaNa2(Mg3Al2)Si7AlO22(OH)2 C 2/m 2/m

66.01.03c.11a Ferronyboite! NaNa2(Fe)3Al2(Si7Al)O22(OH)2 C 2/m 2/m

66.01.03c.11b Ferric-ferronyboite! NaNa2(Fe)3(Fe)2(Si7Al)O22(OH)2 C 2/m 2/m

66.01.03c.11c Fluoronyboite! NaNa2(Al2Mg3)(Si7Al)O22(F,OH)2 C 2/m 2/m

66.01.03c.12 Leakeite NaNa2(Mg2Fe2Li)Si8O22(OH)2 C 2/m 2/m

66.01.03c.12a Ferroleakeite! NaNa2(Fe)3(Fe)2Li(Si8O22)(OH)2 C 2/m 2/m

66.01.03c.12b Potassicleakeite! KNa2Mg2Fe2LiSi8O22(OH)2 C 2/m 2/m

66.01.03c.13 Kornite Na(CaNa)Fe4(Al,Fe)Si7AlO22(OH)2 C 2/m 2/m

66.01.03c.14 Ungarettiite NaNa2(Mn2Mn3)Si8O22O2 C 2/m 2/m

66.01.03c.15 Fluoro-ferroleakeite NaNa2(Fe2Fe2Li)Si8O22F2 C 2/m 2/m

66.01.03c.16 Obertiite! NaNa2(Mg3FeTi)Si8O22(O,F,OH)2 C 2/m 2/m

66.01.03c.17 Dellaventuraite! NaNa2(Mg2,Mn,Li,Ti)Si8O22O2 C 2/m 2/m

Strunz Class:

09.DE.25 09 - SILICATES (Germanates)

09.D - Inosilicates* Structural terminology according to Liebau (1985)

09.DE -Inosilicates with 2-periodic double chains, Si4O11; amphibole family

09.DE.25 Arfvedsonite NaNa2(Fe4Fe)Si8O22(OH)2 C 2/m 2/m

09.DE.25 Ferroglaucophane []Na2(Fe3Al2)Si8O22(OH)2 C 2/m 2/m

09.DE.25 Crossite? Na2(Mg,Fe)3(Al,Fe)2Si8O22(OH)2 C 2/m 2/m

09.DE.25 Eckermannite NaNa2(Mg4Al)Si8O22(OH)2 C 2/m 2/m

09.DE.25 Glaucophane []Na2(Mg3Al2)Si8O22(OH)2 C 2/m 2/m

09.DE.25 Fluoro-ferroleakeite NaNa2(Fe2Fe2Li)Si8O22F2 C 2/m 2/m

09.DE.25 Ferro-eckermannite NaNa2(Fe4Al)Si8O22(OH)2 C 2/m 2/m

09.DE.25 Ferroleakeite! NaNa2(Fe)3(Fe)2Li(Si8O22)(OH)2 C 2/m 2/m

09.DE.25 Ferronyboite! NaNa2(Fe)3Al2(Si7Al)O22(OH)2 C 2/m 2/m

09.DE.25 Ferric-ferronyboite! NaNa2(Fe)3(Fe)2(Si7Al)O22(OH)2 C 2/m 2/m

09.DE.25 Obertiite! NaNa2(Mg3FeTi)Si8O22(O,F,OH)2 C 2/m 2/m

09.DE.25 Nyboite NaNa2(Mg3Al2)Si7AlO22(OH)2 C 2/m 2/m

09.DE.25 Magnesioriebeckite []Na2[(Mg,Fe)3Fe2]Si8O22(OH)2 C 2/m 2/m

09.DE.25 Kozulite NaNa2Mn4(Fe,Al)Si8O22(OH)2 C 2/m 2/m

09.DE.25 Kornite Na(CaNa)Fe4(Al,Fe)Si7AlO22(OH)2 C 2/m 2/m

09.DE.25 Leakeite NaNa2(Mg2Fe2Li)Si8O22(OH)2 C 2/m 2/m

09.DE.25 Magnesio-arfvedsonite NaNa2(Mg4Fe)Si8O22(OH)2 C 2/m 2/m

09.DE.25 Ungarettiite NaNa2(Mn2Mn3)Si8O22O2 C 2/m 2/m

09.DE.25 Riebeckite []Na2(Fe3Fe2)Si8O22(OH)2 C 2/m 2/m

09.DE.25 Potassicleakeite! KNa2Mg2Fe2LiSi8O22(OH)2 C 2/m 2/m

09.DE.25 Fluoronyboite! NaNa2(Al2Mg3)(Si7Al)O22(F,OH)2 C 2/m 2/m

09.DE.25 Fluoro-magnesio-arfvedsonite! NaNa2(Mg,Fe)4Fe[Si8O22](F,OH)2 C 2/m 2/m

09.DE.25 Potassicarfvedsonite! KNa2Fe4FeSi8O22(OH)2 C 2/m 2/m

09.DE.25 Dellaventuraite! NaNa2(Mg2,Mn,Li,Ti)Si8O22O2 C 2/m 2/m

Other Obertiite Information

References:

NAME( MinRec, v 32, p 218) PHYS. PROP.(MinRec, v 32, p 218) OPTIC PROP.(MinRec, v 32, p 218)

See Also:

Links to other databases for Obertiite :
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
10 - Ruff.Info

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Obertiite

NaNa2(Mg3Fe+++Ti)Si8O22(O,F,OH)2
Dana No: 66.01.03c.16 Strunz No: 09.DE.25
Locality:

Notes: