Aenigmatite
A valid IMA mineral species - grandfathered
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About Aenigmatite
Formula:
Na4[Fe2+10Ti2]O4[Si12O36]
Colour:
Velvet-black
Lustre:
Greasy
Hardness:
5½ - 6
Crystal System:
Triclinic
Member of:
Name:
From the Greek αίνιγμα ("aenigma"), "a riddle", alluding to the enigmatic, uncertain (at that time) chemical composition of the mineral. Named in 1865 by Breithaupt.
Unique Identifiers
Mindat ID:
33
Long-form identifier:
mindat:1:1:33:4
IMA Classification of Aenigmatite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Na4(Fe2+10Ti4+2)O4[Si12O36]
First published:
1865
Approval history:
Approved: IMA 1967 special procedure.
Classification of Aenigmatite
9.DH.40
9 : SILICATES (Germanates)
D : Inosilicates
H : Inosilicates with 4-periodic single chains, Si4O12
9 : SILICATES (Germanates)
D : Inosilicates
H : Inosilicates with 4-periodic single chains, Si4O12
69.2.1a.1
69 : INOSILICATES Chains with Side Branches or Loops
2 : Chains with Side Branches or Loops with P>2
69 : INOSILICATES Chains with Side Branches or Loops
2 : Chains with Side Branches or Loops with P>2
14.9.34
14 : Silicates not Containing Aluminum
9 : Silicates of Ti
14 : Silicates not Containing Aluminum
9 : Silicates of Ti
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 for Standard |
|---|---|---|
| Aen | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Aen | 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 Aenigmatite
Greasy
Transparency:
Translucent, Opaque
Colour:
Velvet-black
Comment:
In thin section, reddish brown to black.
Streak:
Reddish brown
Hardness:
5½ - 6 on Mohs scale
Tenacity:
Brittle
Cleavage:
Distinct/Good
{010} {100}
{010} {100}
Fracture:
Irregular/Uneven
Optical Data of Aenigmatite
Type:
Biaxial (+)
RI values:
nα = 1.78 - 1.8 nβ = 1.8 - 1.82 nγ = 1.87 - 1.9
2V:
Measured: 27° to 55°, Calculated: 56° to 60°
Max. Birefringence:
δ = 0.090 - 0.100
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:
Very High (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 biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
single
Optical Extinction:
Y = b; Z ∧ c = 45°.
Chemistry of Aenigmatite
Mindat Formula:
Na4[Fe2+10Ti2]O4[Si12O36]
Element Weights:
Common Impurities:
Al,Mn,Mg,Ca,K,Cl
Chemical Analysis
Oxide wt%:
| 1 | 2 | |
|---|---|---|
| SiO2 | 38.42 % | 38.73 % |
| TiO2 | 8.77 % | 8.95 % |
| ZrO2 | 0.06 % | 0.08 % |
| Al2O3 | 1.95 % | 1.98 % |
| Fe2O3 | 4.58 % | 3.92 % |
| FeO | 34.6 % | 34.3 % |
| MnO | 1.76 % | 1.53 % |
| MgO | 1.30 % | 1.50 % |
| ZnO | 0.06 % | 0.06 % |
| CaO | 1.44 % | 1.21 % |
| Na2O | 6.06 % | 6.27 % |
| K2O | 0.02 % | 0.10 % |
| Total: | 99.02 % | 98.63 % |
Sample references:
| ID | Locality | Reference | Notes |
|---|---|---|---|
| 1 | Kariåsen, Vesterøya, Sandefjord, Vestfold, Norway | XRF analysis and wet chemical analysis (Fe2+). Analyst: Alf Olav Larsen | |
| 2 | Buer, Vesterøya, Sandefjord, Vestfold, Norway | XRF analysis and wet chemical analysis (Fe2+). Analyst: Alf Olav Larsen |
Crystallography of Aenigmatite
Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 10.415(1) Å, b = 10.840(1) Å, c = 8.931(1) Å
α = 105.107(4)°, β = 96.610(5)°, γ = 125.398(4)°
α = 105.107(4)°, β = 96.610(5)°, γ = 125.398(4)°
Ratio:
a:b:c = 0.961 : 1 : 0.824
Unit Cell V:
746.8 ų
Morphology:
Crystals, prismatic after[001], to 10 cm; as irregular segregations.
Twinning:
By rotation (011) or about [010] of
the pseudomonoclinic cell; polysynthetic.
the pseudomonoclinic cell; polysynthetic.
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) |
|---|---|---|---|---|---|---|---|
| 0007269 | Aenigmatite | Grew E S, Halenius U, Pasero M (2008) The crystal-chemistry of aenigmatite revisited: electron microprobe data, structure refinement and Mossbauer spectroscopy of aenigmatite from Vesteroya (Norway) European Journal of Mineralogy 20 983-991 | 2008 | Vesteroya, Vestfold District, Norway | 0 | 293 | |
| 0002350 | Aenigmatite | Yang H, Konzett J (2000) High-pressure synthesis of Na2Mg6Si6O18(OH)2 - a new hydrous silicate phase isostructural with aenigmatite American Mineralogist 85 259-262 |  | 2000 | 0 | 293 | |
| 0002100 | Aenigmatite | Gasparik T, Parise J B, Reeder R J, Young V G, Wilford W S (1999) Composition, stability, and structure of a new member of the aenigmatite group, Na2Mg4+xFe2-2xSi6+xO20, synthesized at 13-14 GPa American Mineralogist 84 257-266 | | 1999 | 0 | 293 | |
| 0000225 | Aenigmatite | Cannillo E, Mazzi F, Fang J H, Robinson P D, Ohya Y (1971) The crystal structure of aenigmatite sample FRO American Mineralogist 56 427-446 | | 1971 | 0 | 293 | |
| 0000224 | Aenigmatite | Cannillo E, Mazzi F, Fang J H, Robinson P D, Ohya Y (1971) The crystal structure of aenigmatite sample CM American Mineralogist 56 427-446 | | 1971 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.09 Å | (very strong) |
| 3.145 Å | (very strong) |
| 2.706 Å | (strong) |
| 2.547 Å | (strong) |
| 2.937 Å | (medium strong) |
| 2.119 Å | (medium strong) |
| 2.414 Å | (medium) |
Comments:
Kola Peninsula, Russia.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 2: Planetesimal differentiation and alteration | 4.566-4.550 |
| 6 : Secondary asteroid phases | 4.566-4.560 |
| Stage 3a: Earth’s earliest Hadean crust | >4.50 |
| 9 : Lava/xenolith minerals (hornfels, sanidinite facies) | |
| Stage 4a: Earth’s earliest continental crust | >4.4-3.0 |
| 19 : Granitic intrusive rocks | |
| 20 : Acidic volcanic rocks | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks | |
| 36 : Carbonatites, kimberlites, and related igneous rocks |
Geological Setting:
A primary constituent in sodium-rich alkalic volcanics, pegmatites, and other silica-poor igneous rocks.
Type Occurrence of Aenigmatite
Co-Type Localities:
Place of Conservation of Type Material:
Mining Academy, Freiberg, Germany, 29166.
Synonyms of Aenigmatite
Other Language Names for Aenigmatite
Dutch:Aenigmatiet
French:Aenigmatite
German:Aenigmatit
Cosyrit
Kölbingit
Cosyrit
Kölbingit
Italian:Enigmatite
Norwegian:Ænigmatitt
Enigmatitt
Enigmatitt
Russian:Энигматит
Spanish:Aenigmatita
Cosyrita
Kölbingita
Cosyrita
Kölbingita
Relationship of Aenigmatite to other Species
Member of:
Other Members of Aenigmatite Group:
| Krinovite | Na2Mg4Cr3+2(Si6O18)O2 | Tric. 1 : P1 |
| 'UM1991-29-SiO:FeMgNa' | Na4(Mg5Fe3+7)O4[Si9Fe3+3O36] | |
| Wilkinsonite | Na2Fe2+4Fe3+2(Si6O18)O2 | Tric. 1 : P1 |
Common Associates
Associations Based on Photo Data:
| 27 photos of Aenigmatite associated with Aegirine | NaFe3+Si2O6 |
| 22 photos of Aenigmatite associated with Eudialyte | Na15Ca6Fe3Zr3Si(Si25O73)(O,OH,H2O)3(Cl,OH)2 |
| 21 photos of Aenigmatite associated with Microcline | K(AlSi3O8) |
| 18 photos of Aenigmatite associated with Astrophyllite | K2NaFe2+7Ti2[Si4O12]2O2(OH)4F |
| 10 photos of Aenigmatite associated with Nepheline | Na3K(Al4Si4O16) |
| 8 photos of Aenigmatite associated with Quartz | SiO2 |
| 8 photos of Aenigmatite associated with Opal | SiO2 · nH2O |
| 5 photos of Aenigmatite associated with Titanite | CaTiO(SiO4) |
| 5 photos of Aenigmatite associated with Ferro-katophorite | Na(CaNa)(Fe2+4Al)(AlSi7O22)(OH)2 |
| 5 photos of Aenigmatite associated with Albite | Na(AlSi3O8) |
Related Minerals - Strunz-mindat Grouping
| 9.DH. | Devilliersite | Ca4Ca2Fe3+10O4[(Fe3+10Si2)O36] |
| 9.DH. | 'Gageite-2M' | (Mn,Mg,Zn)42Si16O54(OH)40 |
| 9.DH. | Bavsiite | Ba2V2O2[Si4O12] |
| 9.DH. | Yuzuxiangite | Sr3Fe3+(Si2O6)2(OH) · 3H2O |
| 9.DH. | Louisfuchsite | Ca2(Mg4Ti2)(Al4Si2)O20 |
| 9.DH.05 | Leucophanite | NaCaBeSi2O6F |
| 9.DH.10 | Ohmilite | Sr3(Ti,Fe3+)(Si4O12)(O,OH) · 2-3H2O |
| 9.DH.15 | Haradaite | SrVSi2O7 |
| 9.DH.15 | Suzukiite | BaVSi2O7 |
| 9.DH.20 | Shcherbakovite | (K,Ba)KNa(Ti,Nb)2(Si4O12)O2 |
| 9.DH.20 | Batisite | BaNaNaTi2(Si4O12)O2 |
| 9.DH.20 | Noonkanbahite | BaKNaTi2(Si4O12)O2 |
| 9.DH.25 | Taikanite | Sr3BaMn2+2(Si4O12)O2 |
| 9.DH.30 | Krauskopfite | BaSi2O5 · 3H2O |
| 9.DH.35 | Gageite | Mn21(Si4O12)2O3(OH)20 |
| 9.DH.35 | Balangeroite | (Mg,Fe2+,Fe3+,Mn2+)42Si16O54(OH)40 |
| 9.DH.40 | Kuratite | Ca2(Fe2+5Ti)O2[Si4Al2O18] |
| 9.DH.40 | Dorrite | Ca4(Mg3Fe3+9)O4(Si3Al8Fe3+O36) |
| 9.DH.40 | Serendibite | Ca4[Mg6Al6]O4[Si6B3Al3O36] |
| 9.DH.40 | Rhönite | Ca4[Mg8Fe3+2Ti2]O4[Si6Al6O36] |
| 9.DH.40 | Khesinite | Ca4(Mg3Fe3+9)O4(Fe3+9Si3)O36 |
| 9.DH.40 | 'UM1991-29-SiO:FeMgNa' | Na4(Mg5Fe3+7)O4[Si9Fe3+3O36] |
| 9.DH.40 | Høgtuvaite | Ca4[Fe2+6Fe3+6]O4[Si8Be2Al2O36] |
| 9.DH.40 | 'Leucorhönite' | Ca2(Mg,Fe3+,Al)6(Si,Al)6O20 |
| 9.DH.40 | Welshite | Ca4Mg9Sb3O4[Si6Be3AlFe2O36] |
| 9.DH.40 | Wilkinsonite | Na2Fe2+4Fe3+2(Si6O18)O2 |
| 9.DH.40 | Krinovite | Na2Mg4Cr3+2(Si6O18)O2 |
| 9.DH.40 | Makarochkinite | (Ca,Na)4[Fe2+8Fe3+2Ti2]O4[Si8Be2Al2O36] |
| 9.DH.45 | Sapphirine | Mg4(Mg3Al9)O4[Si3Al9O36] |
| 9.DH.50 | Khmaralite | (Mg,Al,Fe)16[(Al,Si,Be)12O36]O4 |
| 9.DH.55 | 'UM1988-26-SiO:AlMg' | Mg4Al2O[Si3Al2O15] |
| 9.DH.55 | Surinamite | (Mg,Fe)3Al4BeSi3O16 |
| 9.DH.60 | Deerite | Fe2+6Fe3+3(Si6O17)O3(OH)5 |
| 9.DH.65 | Taneyamalite | (Na,Ca)Mn2+12(Si,Al)12(O,OH)44 |
| 9.DH.65 | Howieite | Na(Fe2+,Fe3+,Al,Mg)12(Si6O17)2(O,OH)10 |
| 9.DH.70 | Johninnesite | Na2Mn2+9Mg7(OH)8[AsO4]2[Si6O17]2 |
| 9.DH.75 | Agrellite | NaCa2Si4O10F |
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.
Aenigmatite in petrology
An essential component of rock names highlighted in red, an accessory component in rock names highlighted in green.
Internet Links for Aenigmatite
mindat.org URL:
https://www.mindat.org/min-33.html
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References for Aenigmatite
Reference List:
Foerstner, H. (1881) Ueber Cossyrit, ein Mineral aus den Liparitlaven der Insel Pantellaria. Zeitschrift für Kristallographie, 5 (4). 348 doi:10.1524/zkri.1881.5.4.348(as Cossyrit)
Kelsey, C. H., McKie, Duncan (1964) The unit-cell of aenigmatite. Mineralogical Magazine and Journal of the Mineralogical Society, 33 (266) 986-1001 doi:10.1180/minmag.1964.033.266.06
Cannillo, E., Mazzi, F ., Fang, J. H., Robinson, Paul D., Ohya, and Y. (1971) The crystal structure of aenigmatite. American Mineralogist, 56 (3-4) 427-446
Borley, G. D. (1976) Ænigmatite from an Ægirine—Riebeckite granite, Liruei Complex, Nigeria. Mineralogical Magazine, 40 (314) 595-598 doi:10.1180/minmag.1976.040.314.06
Jensen, B. B. (1996) Solid solution among members of the aenigmatite group. Mineralogical Magazine, 60 (403) 982-986 doi:10.1180/minmag.1996.060.403.14
Kunzmann, Thomas (1999) The aenigmatite-rhönite mineral group. European Journal of Mineralogy, 11 (4) 743-756 doi:10.1127/ejm/11/4/0743
Localities for Aenigmatite
Showing 351 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.
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Kangerluarsuk Fjord, Ilímaussaq complex, Kujalleq, Greenland