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Oftedalite (Oftedalit)

Collectors Summary

Color weiß bis grau
Streak color weiß
Lustre Glasglanz
Hardness (Mohs) 6
Cleavages undeutlich parallel zu (001)
Fracture muschelig
Crystal System hexagonal, P6/mcc
Morphology kurzprismatische Kristalle bis 100 µm im Durchmesser, auch als Umwandlungsmineral neben ander Sc-haltigen Mineralien

Chemism

Chemical formula

KSc2(Be,Al)3Si12O30

Additional chem. information

Milarit Gruppe

Chemical composition

Aluminium, Beryllium, Scandium, Silicium, Kalium, Sauerstoff

Unit weight: 986.532955425 u; Number of atoms in the formula: 48

Info

Empirical formula:

KSc2(Be0.75Al0.25)3Si12O30

Element

Symbol

Weight%

Atoms

Atoms%

Atom weight (u)

Sum weight (u)
Beryllium

Be

2.06

2.25

4.69

9.0121823

20.2774102
Oxygen

O

48.65

30

62.50

15.9994300

479.9829000
Aluminium

Al

2.05

0.75

1.56

26.9815382

20.2361537
Silicon

Si

34.16

12

25.00

28.0855300

337.0263600
Potassium

K

3.96

1

2.08

39.0983100

39.0983100
Scandium

Sc

9.11

2

4.17

44.9559108

89.9118216

Analysis wt%

SiO2 : 73.32, Al2O3 : 0.47, Sc2O3 : 6.77, MnO : 1.32, BeO : 7.41, CaO : 4.49, K2O : 4.71 (Ref: Canadian Mineralogist 2006)

Strunz 9th edition incl. updates

9.CM.05

9: Silikate (Germanate)
C: Ringsilikate (Cyclosilikate)
M: ~[Si6O18]12- sechser-Doppelringe
05:Milarit-Gruppe

Lapis Classification

VIII/E.22-018

VIII: SILIKATE
E: Ringsilikate
22: Doppelte Sechserringe [Si12O30] 12-; Milarit/Osumilith-Gruppe

Classification by Hölzel

9.CF.150

9: SILICATES
C: Cyclosilicates
F: ~[Si12O30]12--Rings Milarite-Group

IMA status

anerkannt 2004

Mineral status

anerkanntes Mineral

Optical Properties

Color

weiß bis grau

Streak color

weiß

Lustre

Glasglanz

max. Birefringence

0.003
Birefringence chart\! Oftedalite title=Birefringence chart Oftedalite

Michel-Levy Color Chart viewed according to the maximum birefringence (at 30μm). Mineral color is not taken into account. Click on the image to enlarge or change thickness.

RI value α / ω / n

1.556

RI value γ / ε

1.553

Ri mean

1.555

2V angle

Uniaxial (-)

Pleochroism

keiner

Crystallography

Crystal System

hexagonal

Class (H-M)

6/mmm

Space Group number

192

Space Group

P6/mcc

Cell parameters a (Å)

10.097

Cell parameters b (Å)

-

Cell parameters c (Å)

13.991

Cell parameters a/b or c/a

1.386

Cell parameters c/b

-

Cell parameters α

90°

Cell parameters β

90°

Cell parameters γ

120°

Z

2

Volumne (ų)

1235.276

X-Ray Powder Diffraction

7.012(4), 5.044(5), 4.097(7), 3.504(5), 3.229(10), 2.880(8), 1.836(4), 1.751(4)
XRD chart Oftedalite

Calculated from d-spacing and intensity at 0.1541838 nm (Cu)

Morphology

kurzprismatische Kristalle bis 100 µm im Durchmesser, auch als Umwandlungsmineral neben ander Sc-haltigen Mineralien

Crystals 3D

Open larger view

Crystal Structure 3D

Open larger view

Physical Properties

Hardness (Mohs)

6

VHN (Hardness Vickers)

730

Density (g/cm³)

2.61 (berechnet)

2.652 ( ρ calc. Mineralienatlas )

Cleavages

undeutlich parallel zu (001)

Fracture

muschelig

Tenacity

spröde

(Co-)Type locality

(Co-)Type locality

Norwegen/Vestfold og Telemark, Provinz/Drangedal/Tørdal/Heftetjern-Pegmatit

References

Canadian Mineralogist 44 (2006), 943

Kristiansen, R. (2005) "Milarittgruppens mineraler i Norge" ["The milarite group minerals in Norway]. Norsk Bergverksmuseums Skrift, 30, 21-29.

Other languages

German

Oftedalit

English

Oftedalite

Traditional Chinese

鈧整柱石

Simplified Chinese

钪整柱石

Alternative Name

English

Scandiomilarite

CNMNC (IMA)-Number

IMA 2003-045a

CNMNC symbol

Symbol

Oft

Locations with GPS information