Oftedalite
A valid IMA mineral species
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About Oftedalite
Formula:
K◻2(ScCa)Be3[Si12O30]
Previously given as K(Sc,Ca,Mn2+)2◻2[(Be,Al)3Si12O30].
The current IMA formula (as of Sept. 2023) shows the A site is 2Sc, but this combination doesn't allow the overall formula to charge balance, and appears to be a typo.
In Gagné & Hawthorne (2016), the A site is instead shown as (ScCa), and this combination does charge balance the overall formula.
The current IMA formula (as of Sept. 2023) shows the A site is 2Sc, but this combination doesn't allow the overall formula to charge balance, and appears to be a typo.
In Gagné & Hawthorne (2016), the A site is instead shown as (ScCa), and this combination does charge balance the overall formula.
Colour:
Greyish white
Lustre:
Vitreous
Hardness:
6
Specific Gravity:
2.614 (Calculated)
Crystal System:
Hexagonal
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."
Type Locality:
Unique combination of elements (status: 04.2024).
Unique Identifiers
Mindat ID:
27498
Long-form identifier:
mindat:1:1:27498:4
IMA Classification of Oftedalite
Classification of Oftedalite
9.CM.05
9 : SILICATES (Germanates)
C : Cyclosilicates
M : [Si6O18]12- 6-membered double rings (sechser-Doppelringe)
9 : SILICATES (Germanates)
C : Cyclosilicates
M : [Si6O18]12- 6-membered double rings (sechser-Doppelringe)
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference |
|---|---|---|
| Oft | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Oft | The Canadian Mineralogist (2019) | The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download |
Physical Properties of Oftedalite
Vitreous
Colour:
Greyish white
Streak:
White
Hardness:
6 on Mohs scale
Tenacity:
Brittle
Cleavage:
Poor/Indistinct
Parallel to {001}
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
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars.
Surface Relief:
Moderate
Pleochroism:
Non-pleochroic
Chemistry of Oftedalite
Mindat Formula:
K◻2(ScCa)Be3[Si12O30]
Previously given as K(Sc,Ca,Mn2+)2◻2[(Be,Al)3Si12O30].
The current IMA formula (as of Sept. 2023) shows the A site is 2Sc, but this combination doesn't allow the overall formula to charge balance, and appears to be a typo.
In Gagné & Hawthorne (2016), the A site is instead shown as (ScCa), and this combination does charge balance the overall formula.
Previously given as K(Sc,Ca,Mn2+)2◻2[(Be,Al)3Si12O30].
The current IMA formula (as of Sept. 2023) shows the A site is 2Sc, but this combination doesn't allow the overall formula to charge balance, and appears to be a typo.
In Gagné & Hawthorne (2016), the A site is instead shown as (ScCa), and this combination does charge balance the overall formula.
Element Weights:
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 V:
1235.3 ų
Z:
2
Morphology:
Hexagonal prisms, with prominent {100} and {001} forms.
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0006096 | Oftedalite | Cooper M A, Hawthorne F C, Ball N A, Cerny P, Kristiansen R (2006) 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 The Canadian Mineralogist 44 943-949 |  | 2006 | Heftetjern pegmatite, Tordal, Norway | 0 | 293 |
CIF Raw Data - click here to close
Epitaxial Relationships of Oftedalite
Epitaxial Minerals:
| Milarite | K(◻H2O)Ca2(Be2Al)[Si12O30] |
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
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.229 Å | (10) |
| 4.097 Å | (7) |
| 5.044 Å | (5) |
| 3.504 Å | (5) |
| 7.012 Å | (4) |
| 1.836 Å | (4) |
| 1.751 Å | (4) |
| 2.735 Å | (3) |
Comments:
Recorded on type material; Format of data: d/Å (I/%) (hkl)
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 34 : Complex granite pegmatites |
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.
Place of Conservation of Type Material:
The Canadian Museum of Nature, Ottawa, Ontario, Canada (H04/98).
Steiermärkisches Landesmuseum, Graz, Austria.
Steiermärkisches Landesmuseum, Graz, Austria.
Geological Setting of Type Material:
Granitic pegmatite.
Associated Minerals at Type Locality:
Synonyms of Oftedalite
Other Language Names for Oftedalite
Relationship of Oftedalite to other Species
Member of:
Other Members of Osumilite Group:
| Agakhanovite-(Y) | K◻2(YCa)Be3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Almarudite | K◻2Mn2+2(Be2Al)[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mmm |
| Aluminosugilite | KNa2Al2Li3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Armenite | Ba(H2O)2Ca2Al3[Al3Si9O30] | Orth. mmm (2/m 2/m 2/m) : Pnna |
| Berezanskite | K◻2Ti2Li3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Brannockite | K◻2Sn2Li3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Chayesite | K◻2Mg2(Mg2Fe3+)[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Darapiosite | KNa2Mn2(Zn2Li)[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Dusmatovite | K(K◻)Mn2+2Zn3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Eifelite | KNa2(MgNa)Mg3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Friedrichbeckeite | K(◻Na)Mg2(Be2Mg)[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Klöchite | K◻2(Fe2+Fe3+)Zn3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P63/mmc |
| Laurentthomasite | K◻2Mg2(Be2Al)[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Merrihueite | K(◻Na)Fe2+2Fe2+3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Milarite | K(◻H2O)Ca2(Be2Al)[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Osumilite | K◻2Fe2+2Al3[Al2Si10O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Osumilite-(Mg) | K◻2Mg2Al3[Al2Si10O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Poudretteite | K◻2Na2B3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Roedderite | K(◻Na)Mg2Mg3[Si12O30] | Hex. 6 m2 : P62c |
| Shibkovite | K(◻K)Ca2Zn3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Sogdianite | K◻2Zr2Li3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Sugilite | KNa2Fe3+2Li3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| Trattnerite | ◻(◻)2Fe3+2Mg3[Si12O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
| UM1990-73-SiO:KMnNaZn | K(KNa0.5◻0.5)(Mn1.5Na0.5)Zn3[Si12O30] | Hex. |
| Unnamed (Mn3+-dominant analog of Sugilite) | KNa2Mn3+2Li3[Si12O30] | |
| Yagiite | Na◻2Mg2Al3[Al2Si10O30] | Hex. 6/mmm (6/m 2/m 2/m) : P6/mcc |
Related Minerals - Strunz-mindat Grouping
| 9.CM. | Agakhanovite-(Y) | K◻2(YCa)Be3[Si12O30] |
| 9.CM.05 | Friedrichbeckeite | K(◻Na)Mg2(Be2Mg)[Si12O30] |
| 9.CM.05 | Laurentthomasite | K◻2Mg2(Be2Al)[Si12O30] |
| 9.CM.05 | UM1990-73-SiO:KMnNaZn | K(KNa0.5◻0.5)(Mn1.5Na0.5)Zn3[Si12O30] |
| 9.CM.05 | Eifelite | KNa2(MgNa)Mg3[Si12O30] |
| 9.CM.05 | Almarudite | K◻2Mn2+2(Be2Al)[Si12O30] |
| 9.CM.05 | Armenite | Ba(H2O)2Ca2Al3[Al3Si9O30] |
| 9.CM.05 | Merrihueite | K(◻Na)Fe2+2Fe2+3[Si12O30] |
| 9.CM.05 | Roedderite | K(◻Na)Mg2Mg3[Si12O30] |
| 9.CM.05 | Shibkovite | K(◻K)Ca2Zn3[Si12O30] |
| 9.CM.05 | Sogdianite | K◻2Zr2Li3[Si12O30] |
| 9.CM.05 | Milarite | K(◻H2O)Ca2(Be2Al)[Si12O30] |
| 9.CM.05 | Berezanskite | K◻2Ti2Li3[Si12O30] |
| 9.CM.05 | Poudretteite | K◻2Na2B3[Si12O30] |
| 9.CM.05 | Darapiosite | KNa2Mn2(Zn2Li)[Si12O30] |
| 9.CM.05 | Chayesite | K◻2Mg2(Mg2Fe3+)[Si12O30] |
| 9.CM.05 | Osumilite-(Mg) | K◻2Mg2Al3[Al2Si10O30] |
| 9.CM.05 | Osumilite | K◻2Fe2+2Al3[Al2Si10O30] |
| 9.CM.05 | Sugilite | KNa2Fe3+2Li3[Si12O30] |
| 9.CM.05 | Trattnerite | ◻(◻)2Fe3+2Mg3[Si12O30] |
| 9.CM.05 | Brannockite | K◻2Sn2Li3[Si12O30] |
| 9.CM.05 | Klöchite | K◻2(Fe2+Fe3+)Zn3[Si12O30] |
| 9.CM.05 | Dusmatovite | K(K◻)Mn2+2Zn3[Si12O30] |
| 9.CM.05 | Yagiite | Na◻2Mg2Al3[Al2Si10O30] |
| 9.CM.9.CM. | Aluminosugilite | KNa2Al2Li3[Si12O30] |
| 9.CM.10 | Faizievite | K2Na(Ca6Na)Ti4Li6[Si6O18]2[Si12O30]F2 |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 4.0383% | 1,252 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
Fluorescence of Oftedalite
None observed
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.
Internet Links for Oftedalite
mindat.org URL:
https://www.mindat.org/min-27498.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Oftedalite
Reference List:
Kristiansen, Roy (2005) Milarittgruppens mineraler i Norge [The minerals of the milarite group in Norway]. Norsk Bergverksmuseum Skrift, 30. 21-29
Cooper, M. A., Hawthorne, F. C., Ball, N. A., Černý, Petr, Kristiansen, Roy (2006) Oftedalite, (ScCa)KBe3Si12O30, a new mineral species of the milarite group from the Heftetjern pegmatite, Tørdal, Norway: description and crystal structure. The Canadian Mineralogist, 44 (4) 943-949 doi:10.2113/gscanmin.44.4.943
Localities for Oftedalite
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Norway (TL) | |
| Kristiansen (2005) +2 other references |
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Heftetjern pegmatite, Tørdal, Drangedal, Telemark, Norway