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Oftedalite

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Formula:
KSc2(Be3AlSi11)O30
System:
Hexagonal
Colour:
Greyish white
Lustre:
Vitreous
Hardness:
6
Member of:
Name:
Named by M.A. Cooper, F.C. Hawthorne, N.A. Ball, P. Černý, R. Kristiansen in 2006 in honor of Ivar Werner Oftedal (1894–1976), Professor of Mineralogy at the Institute of Geology, University of Oslo (1949, Larvik, Norway - 1964), "who contributed extensively to the geochemistry of scandium, and who wrote the first papers on the mineralogy of the Tørdal pegmatites."
This page provides mineralogical data about Oftedalite.


Classification of Oftedalite

Approved
Approval Year:
2004
First Published:
2006
9.CM.05

9 : SILICATES (Germanates)
C : Cyclosilicates
M : [Si6O18]12- 6-membered double rings (sechser-Doppelringe)

Physical Properties of Oftedalite

Vitreous
Colour:
Greyish white
Streak:
White
Hardness (Mohs):
6
Tenacity:
Brittle
Cleavage:
Poor/Indistinct
parallel to {001}
Fracture:
Conchoidal
Density:
2.614 g/cm3 (Calculated)

Optical Data of Oftedalite

Type:
Uniaxial (-)
RI values:
nω = 1.554 - 1.558 nε = 1.551 - 1.555
Max Birefringence:
δ = 0.003
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Pleochroism:
Non-pleochroic

Chemical Properties of Oftedalite

IMA Formula:
KSc2(Be3AlSi11)O30
Elements listed in formula:
Analytical Data:
Results from electron microprobe analysis, Be content calculated per formula unit as n(Be) = 3 – n(Al);
Empirical formula based on 30 oxygen atoms per formula unit
SiO2 (73.32)
Al2O3 (0.47)
Sc2O3 (6.77)
Y2O3 (0.36)
FeO (0.26)
MnO (1.32)
CaO (4.49)
K2O (4.71)
BeO (7.41)

sum 99.11 wt.-%

Crystallography of Oftedalite

Crystal System:
Hexagonal
Class (H-M):
6/mmm (6/m 2/m 2/m) - Dihexagonal Dipyramidal
Space Group:
P6/mcc
Cell Parameters:
a = 10.097 Å, c = 13.991 Å
Ratio:
a:c = 1 : 1.386
Unit Cell Volume:
V 1235.3 ų
Z:
2

Epitaxial Relationships of Oftedalite

Epitaxial Minerals:
MilariteK2Ca4Al2Be4Si24O60 · H2O
Epitaxy Comments:
frequently with very thin crystals of Sc-free milarite up to ~10–20 µm across in parallel orientation on the (001) faces
X-Ray Powder Diffraction Data:
d-spacingIntensity
3.229 (10)
4.097 (7)
5.044 (5)
3.504 (5)
7.012 (4)
1.836 (4)
1.751 (4)
2.735 (3)
Comments:
Recorded on type material; Format of data: d/Å (I/%) (hkl)

Type Occurrence of Oftedalite

General Appearance of Type Material:
short prismatic crystals up to 100 µm in diameter, or as a product of replacement together with other Sc-bearing minerals
Geological Setting of Type Material:
Granitic pegmatite
Empirical Formula:
(Sc0.96Ca0.79Mn2+0.18Fe2+0.04)=2.00K0.98(Be2.91Al0.09)=3.00Si11.98O30

Relationship of Oftedalite to other Species

Member of:
Other Members of Group:
Agakhanovite-(Y)(YCa)□2KBe3Si12O30
AlmaruditeK(□,Na)2(Mn2+,Fe2+,Mg)2(Be,Al)3[Si12O30]
ArmeniteBaCa2Al6Si9O30 · 2H2O
BerezanskiteK□2Li3(Ti,Zr,Sn)2[Si12O30]
Brannockite(K,Na)□2Li3(Sn,Zr,Ti)2[Si12O30]
DarapiositeK(Na,◻,K)2(Li,Zn,Fe)3(Mn,Zr,Y)2[Si12O30]
DusmatoviteK(Na,□)2(Zn,Li)3(Mn2+,Y,Zr)2[Si12O30]
EifeliteKNa3Mg4Si12O30
FriedrichbeckeiteK(□0.5Na0.5)2Mg2Be3Si12O30
Klöchite(□Na)KFe22+Zn3(Si12O30)
Merrihueite(K,Na)2(Fe,Mg)5Si12O30
MilariteK2Ca4Al2Be4Si24O60 · H2O
Osumilite(K,Na)(Fe2+,Mg)2(Al,Fe3+)3(Si,Al)12O30
Osumilite-(Mg)KMg2Al3(Al2Si10)O30
PoudretteiteKNa2B3Si12O30
Roedderite(Na,K)2(Mg,Fe)5Si12O30
ShibkoviteK(□,K,Na)2Zn3Ca2[Si12O30]
SogdianiteK(□,Na)2Li3(Zr,Fe,Ti)2[Si12O30]
SugiliteK(Na,□)2Li3(Fe,Mn,Al,Zr)2[Si12O30]
Trattnerite□(Fe3+,Mg,Fe2+)2(Mg,Fe2+,Fe3+)3(Si12O30)
Yagiite(Na,K)3Mg4(Al,Mg)6(Si,Al)24O60
9.CM.05ArmeniteBaCa2(Al6Si9)O30 · 2H2O
9.CM.05BrannockiteKSn2(Li3Si12)O30
9.CM.05ChayesiteKMg2(Mg2Fe3+Si12)O30
9.CM.05DarapiositeKNa2Mn2(Li2ZnSi12)O30
9.CM.05EifeliteKNa2(MgNa)(Mg3Si12)O30
9.CM.05Merrihueite(K,Na)2(Fe2+,Mg)5Si12O30
9.CM.05MilariteKCa2(Be2AlSi12O30) · xH2O
9.CM.05Osumilite-(Mg)KMg2(Al5Si10)O30
9.CM.05OsumiliteKFe22+(Al5Si10)O30
9.CM.05PoudretteiteKNa2(B3Si12)O30
9.CM.05RoedderiteKNaMg2(Mg3Si12)O30
9.CM.05SogdianiteKZr2(Li3Si12)O30
9.CM.05SugiliteKNa2Fe23+(Li3Si12)O30
9.CM.05YagiiteNaMg2(AlMg2Si12)O30
9.CM.05BerezanskiteKTi2(Li3Si12)O30
9.CM.05DusmatoviteKK2Mn2(Zn2LiSi12)O30
9.CM.05ShibkoviteK2Ca2(Zn3Si12)O30
9.CM.05AlmaruditeK(◻,Na)2(Mn,Fe,Mg)2(Be,Al)3Si12O30
9.CM.05TrattneriteFe23+(Mg3Si12)O30
9.CM.10FaizieviteLi6K2Na(Ca6Na)Ti4(Si6O18)2(Si12O30)F2

Other Names for Oftedalite

Name in Other Languages:
German:Oftedalit
Simplified Chinese:钪整柱石
Traditional Chinese:鈧整柱石

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Oftedalite

Reference List:
ristiansen, R. (2005) Milarittgruppens mineraler i Norge (The milarite group minerals in Norway). Norsk Bergverksmuseums Skrift: 30: 21-29.

Cooper, M.A., Hawthorne, F.C., Ball, N.A., Černý, P., Kristiansen, R. (2006) Oftedalite, (Sc,Ca,Mn2+)2K(Be,Al)3Si12O30, a new member of the milarite group from the Heftetjern pegmatite, Tørdal, Norway: description and crystal structure. Canadian Mineralogist: 44: 943-949.

Locock, A.J., Ercit, T.S., Kjellman, J., Piilonen, C. (2006) New mineral names. American Mineralogist: 91: 1945-1954.

Internet Links for Oftedalite

mindat.org URL:
https://www.mindat.org/min-27498.html
Please feel free to link to this page.

Localities for Oftedalite

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Norway (TL)
 
  • Telemark
    • Drangedal
      • Tørdal
Cooper, M.A., Hawthorne, F.C., Ball, N.A., Černý, P., Kristiansen, R. (2006): Oftedalite, (ScCa)KBe3Si12O30, a new mineral species of the milarite group from the Heftetjern pegmatite, Tørdal, Norway: description and crystal structure. Canadian Mineralogist, 44, 943-949; Kristiansen, R. (2005): Milarittgruppens mineraler i Norge. Norsk Bergverksmuseum Skrifter, 30, 21-29
Mineral and/or Locality  
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