Oftedalite Mineral Data

General Oftedalite Information

Chemical Formula:

(Sc,Ca)2KBe3Si12O30

Composition:

Molecular Weight = 973.03 gm

Potassium 3.94 % K 4.74 % K₂O

Calcium 3.25 % Ca 4.55 % CaO

Yttrium 0.27 % Y 0.35 % Y₂O₃

Scandium 4.44 % Sc 6.80 % Sc₂O₃

Manganese 1.02 % Mn 1.31 % MnO

Beryllium 2.70 % Be 7.48 % BeO

Aluminum 0.25 % Al 0.47 % Al₂O₃

Iron 0.23 % Fe 0.30 % FeO

Silicon 34.58 % Si 73.98 % SiO₂

Oxygen 49.33 % O

______ ______

100.00 % 99.98 % = TOTAL OXIDE

Empirical Formula:

Environment:

Occurs intergrown with Sc-rich milarite in the Heftetjern pegmatite. Milarite group

IMA Status:

Approved IMA 2004 (Dana # Added)

Locality:

Heftetjern pegmatite, about 4.3 km NW of Tørdal, Telemark county, southern Norway. Link to MinDat.org Location Data.

Name Origin:

Named for Ivar Oftedal (1894-1976), former Professor of Mineralogy at the Institute of Geology, University of Oslo, Norway.

Synonym:

IMA2003-045a

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Oftedalite Crystallography

Axial Ratios:

a:c = 1:1.38565

Cell Dimensions:

a = 10.097, c = 13.991, Z = 2; V = 1,235.28 Den(Calc)= 2.62

Crystal System:

Hexagonal - Dihexagonal DipyramidalH-M Symbol (6/m 2/m 2/m) Space Group: P 6/mmc

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

By Intensity(I/I_o): 3.229(1)(104), 2.88(0.8)(114), 4.097(0.7)(112),3.504(0.5)(004), 5.044(0.5)(110), 7.012(0.4)(002), 1.836(0.4)(412), 1.995(0.3)(314), 2.735(0.3)(204),

Crystal Structure:

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Cooper M A , Hawthorne F C , Ball N A , Cerny P , Kristiansen R , The Canadian Mineralogist , 44 (2006) p.943-949, Oftedalite, (Sc,Ca,Mn2+)2 K (Be,Al)3 Si12 O30, a new member of the milarite, group from the Heftetjern pegmatite, Tordal, Norway: description and crystal, structure, Locality: Heftetjern pegmatite, Tordal, Norway

Physical Properties of Oftedalite

Cleavage:

{hk0} Poor

Color:

Grayish white.

Diaphaneity:

Transparent

Fracture:

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

Habit:

Hexagonal - Six-sided crystal shape in cross-section or habit.

Habit:

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

Hardness:

6 - Orthoclase

Luster:

Vitreous (Glassy)

Streak:

colorless

Optical Properties of Oftedalite

Gladstone-Dale:

CI calc= 0.006 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2116,KC= 0.2129
Ncalc = 1.56

Optical Data:

Uniaxial (-), e=1.553, w=1.556, bire=0.0030.

Calculated Properties of Oftedalite

Electron Density:

Bulk Density (Electron Density)=2.59 gm/cc
note: Specific Gravity of Oftedalite =2.62 gm/cc.

Fermion Index:

Fermion Index = 0.04
Boson Index = 0.96

Photoelectric:

PE_Oftedalite= 3.42 barns/electron
U=PE_Oftedalite x r_electron= 8.88 barns/cc.

Radioactivity:

GRapi = 56.26 (Gamma Ray American Petroleum Institute Units)
Concentration of Oftedalite per GRapi unit = 1.78 (%)

Estimated Radioactivity from Oftedalite - barely detectable

Oftedalite Classification

Dana Class:

63.02.01a.19 (63)Cyclosilicate Condensed Rings

(63.02)6-membered rings

(63.02.01a)Milarite - Osumilite group (Milarite - Osumilite subgroup)

63.02.01a.01 Brannockite KSn2Li3Si12O30 P 6/mcc 6/m 2/m 2/m

63.02.01a.02 Chayesite K(Mg,Fe)4Fe(Si12O30) P 6/mcc 6/m 2/m 2/m

63.02.01a.03 Darapiosite KNa2Zr[Li(Mn,Zr)2Si12O30] P 6/mcc 6/m 2/m 2/m

63.02.01a.04 Eifelite KNa3Mg4Si12O30 P 6/mcc 6/m 2/m 2/m

63.02.01a.05 Merrihueite (K,Na)2(Fe,Mg)5Si12O30 P 6/mcc 6/m 2/m 2/m

63.02.01a.06 Osumilite-(Fe) (K,Na)(Fe,Mg)2(Al,Fe)3(Si,Al)12O30 P 6/mcc 6/m 2/m 2/m

63.02.01a.07 Osumilite-(Mg) (K,Na)(Mg,Fe)2(Al,Fe)3(Si,Al)12O30 P 6/mcc 6/m 2/m 2/m

63.02.01a.08 Poudretteite KNa2B3Si12O30 P 6/mcc 6/m 2/m 2/m

63.02.01a.09 Sugilite KNa2(Fe,Mn,Al)2Li3Si12O30 P 6/mcc 6/m 2/m 2/m

63.02.01a.10 Yagiite (Na,K)3Mg4(Al,Mg)6(Si,Al)24O60 P 6/mmc 6/m 2/m 2/m

63.02.01a.11 Dusmatovite K(K,Na,[])(Mn,Y,Zr)2(Zn,Li)3Si12O30 P 6/mcc 6/m 2/m 2/m

63.02.01a.12 Milarite K2Ca4Al2Be4Si24O60•(H2O) P 6/mcc 6/m 2/m 2/m

63.02.01a.13 Sogdianite (K,Na)2(Li,Fe,Al)3ZrSi12O30 P 6/mmm 6/m 2/m 2/m

63.02.01a.14 Roedderite (Na,K)2(Mg,Fe)5Si12O30 P 6₃/mmc 6/m 2/m 2/m

63.02.01a.15 Berezanskite! KLi3Ti2Si12O30 P 6/mcc 6/m 2/m 2/m

63.02.01a.16 Shibkovite! K(Ca,Mn,Na)2(K2-x,[]x)2ZnSi12O30(x~0.8) P 6/mcc 6/m 2/m 2/m

63.02.01a.17 Trattnerite! (Fe,Mg)2(Mg,Fe)3(Si12O30) P 6/mcc 6/m 2/m 2/m

63.02.01a.18 Almarudite! K([],Na)2(Mn,Fe,Mg)2(Be,Al)3[Si12O30] P 6/mcc 6/m 2/m 2/m

63.02.01a.19 Oftedalite! (Sc,Ca)2KBe3Si12O30 P 6/mmc 6/m 2/m 2/m

63.02.01a.20 Klochite ([]1Na1)KFe2Zn3[Si12O30] P 6/mcc 6/m 2/m 2/m

63.02.01a.21 Friedrichbeckeite! K([],Na)Mg2(Be2Mg)Si12O30 P 6/mcc 6/m 2/m 2/m

Strunz Class:

09.CM.05 09 - SILICATES (Germanates)

09.C - Cyclosilicates

09.CM -[Si6O18]12- 6-membered double rings (sechser-Doppelringe)

09.CM.05 Brannockite KSn2Li3Si12O30 P 6/mcc 6/m 2/m 2/m

09.CM.05 Armenite BaCa2Al6Si9O30•2(H2O) Pnc2 mm2

09.CM.05 Berezanskite! KLi3Ti2Si12O30 P 6/mcc 6/m 2/m 2/m

09.CM.05 Dusmatovite K(K,Na,[])(Mn,Y,Zr)2(Zn,Li)3Si12O30 P 6/mcc 6/m 2/m 2/m

09.CM.05 Chayesite K(Mg,Fe)4Fe(Si12O30) P 6/mcc 6/m 2/m 2/m

09.CM.05 Shibkovite! K(Ca,Mn,Na)2(K2-x,[]x)2ZnSi12O30(x~0.8) P 6/mcc 6/m 2/m 2/m

09.CM.05 Eifelite KNa3Mg4Si12O30 P 6/mcc 6/m 2/m 2/m

09.CM.05 Darapiosite KNa2Zr[Li(Mn,Zr)2Si12O30] P 6/mcc 6/m 2/m 2/m

09.CM.05 Merrihueite (K,Na)2(Fe,Mg)5Si12O30 P 6/mcc 6/m 2/m 2/m

09.CM.05 Roedderite (Na,K)2(Mg,Fe)5Si12O30 P 6₃/mmc 6/m 2/m 2/m

09.CM.05 Milarite K2Ca4Al2Be4Si24O60•(H2O) P 6/mcc 6/m 2/m 2/m

09.CM.05 Osumilite-(Fe) (K,Na)(Fe,Mg)2(Al,Fe)3(Si,Al)12O30 P 6/mcc 6/m 2/m 2/m

09.CM.05 Osumilite-(Mg) (K,Na)(Mg,Fe)2(Al,Fe)3(Si,Al)12O30 P 6/mcc 6/m 2/m 2/m

09.CM.05 Poudretteite KNa2B3Si12O30 P 6/mcc 6/m 2/m 2/m

09.CM.05 Sugilite KNa2(Fe,Mn,Al)2Li3Si12O30 P 6/mcc 6/m 2/m 2/m

09.CM.05 Sogdianite (K,Na)2(Li,Fe,Al)3ZrSi12O30 P 6/mmm 6/m 2/m 2/m

09.CM.05 Oftedalite! (Sc,Ca)2KBe3Si12O30 P 6/mmc 6/m 2/m 2/m

09.CM.05 Yagiite (Na,K)3Mg4(Al,Mg)6(Si,Al)24O60 P 6/mmc 6/m 2/m 2/m

09.CM.05 Trattnerite! (Fe,Mg)2(Mg,Fe)3(Si12O30) P 6/mcc 6/m 2/m 2/m

09.CM.05 Almarudite! K([],Na)2(Mn,Fe,Mg)2(Be,Al)3[Si12O30] P 6/mcc 6/m 2/m 2/m

Other Oftedalite Information

References:

NAME( AmMin, v91, p1948) PHYS. PROP.(AmMin, v91, p1948) OPTIC PROP.(AmMin, v91, p1948)

See Also:

Links to other databases for Oftedalite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - GeoScienceWorld
4 - Google Images
5 - Google Scholar
6 - MinDAT
7 - Mineralienatlas (Deutsch)
8 - Online Mineral Museum
9 - QUT Mineral Atlas
10 - Ruff.Info

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Print or Cut-and-Paste your Oftedalite Specimen Label here :

Oftedalite

(Sc,Ca)2KBe3Si12O30
Dana No: 63.02.01a.19 Strunz No: 09.CM.05
Locality:

Notes: