Ekanite
A valid IMA mineral species
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About Ekanite
F. L. D. Ekanayake
Formula:
Ca2ThSi8O20
Colour:
Green in various shades, straw-yellow, dark red, colourless
Lustre:
Vitreous
Hardness:
4½
Specific Gravity:
2.95 - 3.28
Crystal System:
Tetragonal
Name:
Named in honor of Mr. Francis Leo Danvil Ekanayake, [1898, Negombo, Sri Lanka - 1971, London, UK], a gemmologist active at Colombo (Sri Lanka), who first found the material and suspected it was a new mineral.
Visit gemdat.org for Unique Identifiers
Mindat ID:
1361
Long-form identifier:
mindat:1:1:1361:7
Similar Names
| Eggonite | A synonym of Kolbeckite | |
| Ekatite | A valid IMA mineral species | (Fe3+,Fe2+,Zn)12(AsO3)6(AsO3,HSiO4)2(OH)6 |
| Ekmanite | A variety of Stilpnomelane | K4(Fe2+,Mn)48[Si64Al8]O1664(OH)52 · nH2O |
| Okenite | A valid IMA mineral species - grandfathered | Ca10Si18O46 · 18H2O |
| Okenite (of Rink) | A synonym of Wollastonite |
IMA Classification of Ekanite
Approved
IMA Formula:
Ca2Th4+Si8O20
First published:
1961
Classification of Ekanite
9.EA.10
9 : SILICATES (Germanates)
E : Phyllosilicates
A : Single nets of tetrahedra with 4-, 5-, (6-), and 8-membered rings
9 : SILICATES (Germanates)
E : Phyllosilicates
A : Single nets of tetrahedra with 4-, 5-, (6-), and 8-membered rings
72.1.1.1
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
1 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with 4-membered rings
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
1 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with 4-membered rings
14.16.16
14 : Silicates not Containing Aluminum
16 : Silicates of U
14 : Silicates not Containing Aluminum
16 : Silicates of U
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Ek | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Pronunciation of Ekanite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Ekanite
Vitreous
Colour:
Green in various shades, straw-yellow, dark red, colourless
Streak:
White
Hardness:
4½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Distinct/Good
Distinct on {101}, indistinct on {001}
Distinct on {101}, indistinct on {001}
Fracture:
Irregular/Uneven
Density:
2.95 - 3.28 g/cm3 (Measured) 3.36 g/cm3 (Calculated)
Optical Data of Ekanite
Type:
Uniaxial (-)
RI values:
nω = 1.58 nε = 1.568
Max. Birefringence:
δ = 0.012
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. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
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. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Moderate (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized uniaxial interference figure - the conoscopic
(convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis
centred and vertical. The coloured rings are isochromatics, computed with the
same physics as the Michel-Lévy bar above; the dark cross is the isogyre.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
Chemistry of Ekanite
Mindat Formula:
Ca2ThSi8O20
Element Weights:
Elements listed:
Common Impurities:
U,Fe,Pb,Al,Mn,Pb,Mg
Crystallography of Ekanite
Crystal System:
Tetragonal
Class (H-M):
422 - Trapezohedral
Space Group:
I422
Cell Parameters:
a = 7.483(3) Å, c = 14.893(6) Å
Ratio:
a:c = 1 : 1.99
Unit Cell V:
833.94 ų (Calculated from Unit Cell)
Z:
2
Comment:
Very often metamict.
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Display Options
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View
CIF File Best | x | y | z | a | b | c
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Rotation
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Labels
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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) |
|---|---|---|---|---|---|---|---|
| 0005184 | Ekanite | Szymanski J T, Owens D R, Roberts A C, Ansell H G, Chao G Y (1982) A mineralogical study and crystal-structure determination of nonmetamict ekanite, ThCa2Si8O20 The Canadian Mineralogist 20 65-75 |  | 1982 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 7.45 Å | (58) |
| 6.70 Å | (61) |
| 4.14 Å | (100) |
| 3.343 Å | (96) |
| 3.265 Å | (65) |
| 2.642 Å | (54) |
| 1.796 Å | (26) |
Comments:
Very often metamict.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 3a: Earth’s earliest Hadean crust | >4.50 |
| 9 : Lava/xenolith minerals (hornfels, sanidinite facies) | |
| Near-surface Processes | |
| 26 : Hadean detrital minerals | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Type Occurrence of Ekanite
Place of Conservation of Type Material:
Canadian Geological Survey, Ottawa, Canada, 62722.
The Natural History Museum, London, England, 1961, 472.
National Museum of Natural History, Washington, D.C., USA, 148771.
The Natural History Museum, London, England, 1961, 472.
National Museum of Natural History, Washington, D.C., USA, 148771.
Other Language Names for Ekanite
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 9.EA. | Hydroxymcglassonite-(K) | KSr4Si8O20(OH) · 8H2O |
| 9.EA. | Miyawakiite-(Y) | ◻Y4Fe2(Si8O20)(CO3)4(H2O)3 |
| 9.EA. | Bussyite-(Y) | (Y,REE,Ca)3(Na,Ca)6MnSi9Be5(O,OH,F)34 |
| 9.EA. | Hydroxyapophyllite-(NH4) | (NH4)Ca4(Si8O20)(OH)(H2O)8 |
| 9.EA. | Fluorapophyllite-(NH4) | NH4Ca4(Si8O20)F · 8H2O |
| 9.EA.05 | Gillespite | BaFe2+Si4O10 |
| 9.EA.05 | Cuprorivaite | CaCuSi4O10 |
| 9.EA.05 | Wesselsite | SrCuSi4O10 |
| 9.EA.05 | Effenbergerite | BaCuSi4O10 |
| 9.EA.07 | Fluorapophyllite-(Cs) | CsCa4(Si8O20)F · 8H2O |
| 9.EA.15 | Fluorapophyllite-(Na) | NaCa4(Si8O20)F · 8H2O |
| 9.EA.15 | Fluorapophyllite-(K) | KCa4(Si8O20)(F,OH) · 8H2O |
| 9.EA.15 | Hydroxyapophyllite-(K) | KCa4(Si8O20)(OH,F) · 8H2O |
| 9.EA.20 | Magadiite | Na2Si14O29 · 11H2O |
| 9.EA.25 | Dalyite | K2ZrSi6O15 |
| 9.EA.25 | Davanite | K2TiSi6O15 |
| 9.EA.30 | Sazhinite-(La) | Na3La[Si6O15] · 2H2O |
| 9.EA.30 | Sazhinite-(Ce) | Na3CeSi6O15 · 2H2O |
| 9.EA.35 | Armstrongite | CaZr[Si6O15] · 3H2O |
| 9.EA.40 | Okenite | Ca10Si18O46 · 18H2O |
| 9.EA.45 | Perettiite-(Y) | Y2Mn4FeSi2B8O24 |
| 9.EA.45 | Nekoite | Ca3Si6O15 · 7H2O |
| 9.EA.45 | Badakhshanite-(Y) | Y2Mn4Al(Si2B7BeO24) |
| 9.EA.47 | Shlykovite | KCa[Si4O9(OH)] · 3H2O |
| 9.EA.50 | Diegogattaite | Na2CaCu2Si8O20 · H2O |
| 9.EA.50 | Cavansite | Ca(VO)Si4O10 · 4H2O |
| 9.EA.52 | Yangite | PbMnSi3O8 · H2O |
| 9.EA.55 | Pentagonite | Ca(VO)Si4O10 · 4H2O |
| 9.EA.60 | Penkvilksite | Na4Ti2Si8O22 · 4H2O |
| 9.EA.60 | Tumchaite | Na2Zr(Si4O11) · 2H2O |
| 9.EA.65 | Nabesite | Na2BeSi4O10 · 4H2O |
| 9.EA.70 | Ajoite | (K,Na)Cu7AlSi9O24(OH)6 · 3H2O |
| 9.EA.75 | Zeravshanite | Na2Cs4Zr3[Si18O45]*2H2O |
| 9.EA.80 | Bussyite-(Ce) | (Ce,REE)3(Na,H2O)6MnSi9Be5(O,OH)30F4 |
| 9.EA.85 | Plumbophyllite | Pb2Si4O10 · H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 27.0799% | 1,083,196 | α, β, γ |
| Potassium (K) | 0.0000% | 0 | 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
Other Information
Notes:
Radioactive
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 Ekanite
mindat.org URL:
https://www.mindat.org/min-1361.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Ekanite
Reference List:
Anderson, B. W., Claringbull, G. F., Davis, R. J., Hill, D. K. (1961) Ekanite, a New Metamict Mineral from Ceylon. Nature, 190 (4780) 997 doi:10.1038/190997a0
IMA (1967) International Mineralogical Association: Commission on New Minerals and Mineral Names. Mineralogical Magazine and Journal of the Mineralogical Society, 36 (277) 131-136 doi:10.1180/minmag.1967.036.277.20
Perrault, G., Richard, P. (1973) L'ekanite de St-Hilaire, P.Q. The Canadian Mineralogist, 11 (5) 913-929
Szymański, J. T. (1981) The crystal structure of ekanite, ThCa2Si8O20. Acta Crystallographica Section A Foundations of Crystallography, 37. doi:10.1107/s0108767381093884
Szymański, J. T., Owens, D. R., Roberts, A. C., Ansell, H. G., Chao, G. Y. (1982) A mineralogical study and crystal structure determination of nonmetamict ekanite ThCa2Si8O20. The Canadian Mineralogist, 20 (1) 65-75
Perrault, G., Szymański, J. T. (1982) Steacyite, a new name and a re-evaluation of the nomenclature of "ekanite"-group minerals. The Canadian Mineralogist, 20 (1) 59-63
Dunn, Pete J., Fleischer, Michael, Burns, Roger G., Pabst, Adolf (1983) New mineral names. American Mineralogist, 68 (3-4) 471-475
Della Ventura, Giancario; Maras, Adriana; Parodi, Gian Carlo; Della Ventura, Giancarlo (1986) Nonmetamict U-rich ekanite from Pitigliano (Tuscany, Italy). Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, S. 8 Vol. 80 (7-12). 585-592
Evans, R. J., Groat, L. A. (2012) Structure and topology of dumortierite and dumortierite-like materials. The Canadian Mineralogist, 50 (5) 1197-1231 doi:10.3749/canmin.50.5.1197
Nasdala, Lutz, Corfu, Fernando, Blaimauer, Doris, Chanmuang, Chutimun, Ruschel, Katja, Škoda, Radek, Wildner, Manfred, Wirth, Richard, Zeug, Manuela, Zoysa, E. Gamini (2017) Neoproterozoic amorphous “ekanite” (Ca2Th0.9U0.1Si8O20) from Okkampitiya, Sri Lanka: A metamict gemstone with excellent lead-retention performance. Geology, 45 (10) 919-922 doi:10.1130/g39334.1
Sameera, K. A. Geeth; Hauzenberger, Christoph A.; Fernando, G. W. A. Rohan; Škoda, Radek; Dharmapriya, Prasanna L.; Chanmuang N., Chutimun; Nasdala, Lutz (2026) Formation of ekanite in “antiskarn” by carbonatitic melt infiltration into charnockitic gneiss, Ampegama, southwestern Highland Complex, Sri Lanka. Contributions to Mineralogy and Petrology, 181 (7). p.52. doi:10.1007/s00410-026-02330-z
Localities for Ekanite
Showing 29 localities.
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.
Australia | |
| Anenburg et al. (2018) |
Canada | |
| GSC database: XRD only +1 other reference |
| Richard A.J. (1971) +2 other references |
| Szymański et al. (1982) +1 other reference |
| Szymański et al. (1982) | |
Chad | |
| Olivier et al. (2021) |
Germany | |
| Hanneberg et al. (2009) +1 other reference |
Greenland | |
| Cegiełka et al. (2019) |
Italy | |
| Russo et al. (2013) |
| Caponera et al. (2007) |
| Gianfagna et al. (1988) | |
| Gresta et al. (2002) | |
| |
| Carlini et al. (2017) |
| Marchesini et al. (2025) +1 other reference |
| Bedogné et al. (1994) | |
| Liotti (1991) |
| Biagioni (2016) |
Kyrgyzstan | |
| Pautov et al. (2013) |
Myanmar | |
| Pavel M. Kartashov analytical data |
Portugal | |
| Samples collected by Luigi Chiappino ... +1 other reference |
South Korea | |
| 조남후 et al. (2013) +1 other reference |
Sri Lanka | |
| Dissanayake et al. (2000) |
| Nature 190 (1961) |
| Sameera et al. (2026) |
| Dr. Jaroslav Hyrsl specimens +2 other references |
USA | |
| Dunning et al. (2003) |
| Walstrom (n.d.) |
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Case Collina, Pitigliano, Grosseto Province, Tuscany, Italy