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Aegirine

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Ægir
Formula:
NaFe3+Si2O6
System:
Monoclinic
Colour:
Dark green to greenish ...
Lustre:
Vitreous
Hardness:
6
Name:
First described as acmit by P. H. Ström (1821) from Rundemyr, Øvre Eiker, Buskerud, Norway for a mineral earlier mentioned shortly by Strøm (1784, as "crystalliseret hornsteen eller brun kantet og riflet Schoel i quarz" (crystallized hornstone or brownish angular and grooved schorl in quartz)). Ström (1821) recognized it as a new mineral and suggested the name wernerin, after the german geologist, Abraham Gottlob Werner. But Berzelius (1821), who analyzed the mineral, named it achmit after the greek αχμη, spear point, due to the habit of the crystals.

Later, in 1834, the priest and mineralogist Hans Morten Thrane Esmark found a new mineral on Låven, Langesundsfjorden, Norway which was described and given the name aegirine, after Ægir (Aegir), the sea god in Norse mythology because the type location was along the sea shore (Berzelius 1835). Acmite and aegirine were first believed to be two separate species, one belonging to the amphiboles (acmite) and the other to the pyroxenes (aegirine). This was the case until 1871 when G. Tschermak put forward evidence that acmite and aegirine both belonged to the pyroxenes and are the same mineral. Acmite has been considered as a variety of aegirine (historically acmite had priority, so it should have been the other way around).
Pyroxene Group. Clinopyroxene Subgroup.
Both acmite and aegirine have been used as designations of pyroxenes close to NaFe3+Si2O6 in composition. Acmite has also often been used to refer to the brown variety with pointed terminations (usually {221} and {661}), while aegirine has been reserved for the green to green-black colour varieties. Acmite has also been used to refer to the NaFe3+Si2O6 molecule, the so-called acmite-molecule in pyroxenes. In 1988 acmite was formally discredited as a separate species, and aegirine was used as a name for the end member NaFe3+Si2O6 (Morimoto 1988).

However, at the Rundemyr locality, the TL, both brownish and green-black varieties occur as intergrowths. Raade has shown that the green aegirine from Rundemyr has a higher content of FeO, TiO2, MnO and CaO and a lower content of Fe2O3 than the brown acmite (Raade 2010).

The deep colour typical for most aegirines is though to be due to charge transfer transitions, mainly Fe2+-Ti4+, but also Fe2+-Fe3+, and crystal field transitions related to Fe2+. A peculiar material that is colourless in thin section is described from Bayan Obo, China (Ribeiro Da Costa et al., 2014).


Visit gemdat.org for gemological information about Aegirine.

Classification of Aegirine

Approved, 'Grandfathered' (first described prior to 1959)
8/F.01-140
9.DA.25

9 : SILICATES (Germanates)
D : Inosilicates
A : Inosilicates with 2-periodic single chains, Si2O6; pyroxene family
65.1.3c.2

65 : INOSILICATES Single-Width,Unbranched Chains,(W=1)
1 : Single-Width Unbranched Chains, W=1 with chains P=2
14.20.2

14 : Silicates not Containing Aluminum
20 : Silicates of Fe and alkali metals
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Type Occurrence of Aegirine

Occurrences of Aegirine

Geological Setting:
Common in alkalic igneous rocks, carbonatites, and pegmatites; from regionally metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites; authigenic in some shales and marls.

Physical Properties of Aegirine

Vitreous
Diaphaneity (Transparency):
Transparent, Opaque
Comment:
Slightly resinous
Colour:
Dark green to greenish black, reddish brown, black
Comment:
bright green to yellow-green in thin section
Streak:
Pale yellowish grey
Hardness (Mohs):
6
Tenacity:
Brittle
Cleavage:
Distinct/Good
Good on {110}
Parting:
on {100}
Fracture:
Irregular/Uneven
Density:
3.5 - 3.6 g/cm3 (Measured)    3.576 g/cm3 (Calculated)

Crystallography of Aegirine

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Cell Parameters:
a = 9.658Å, b = 8.795Å, c = 5.294Å
β = 107.42°
Ratio:
a:b:c = 1.098 : 1 : 0.602
Unit Cell Volume:
V 429.06 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Prismatic crystals, showing 110, with blunt to steep terminations, to 35 cm, striated lengthwise, can be bent or twisted. In sprays of acicular crystals, fibrous, in radial concretions.
Twinning:
Simple and lamellar on {100}
Comment:
On synthetic material.

Crystallographic forms of Aegirine

Crystal Atlas:
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Aegirine no.35 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Aegirine

Type:
Biaxial (-)
RI values:
nα = 1.720 - 1.778 nβ = 1.740 - 1.819 nγ = 1.757 - 1.839
2V:
Measured: 60° to 90°, Calculated: 68° to 84°
Max Birefringence:
δ = 0.037 - 0.061
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Very High
Dispersion:
moderate to strong r > v
Pleochroism:
Visible
Comments:
X= emerald green, deep green
Y= grass green, deep green, yellow
Z= brownish green, green, yellowish brown, yellow
Comments:
Biaxial + for Ca,Mg,Fe varieties.

Chemical Properties of Aegirine

Formula:
NaFe3+Si2O6
All elements listed in formula:
Common Impurities:
Al,Ti,V,Mn,Mg,Ca,K,Zr,Ce

Relationship of Aegirine to other Species

Other Members of Group:
Aegirine-augite(Na,Ca)(Fe3+,Fe2+,Mg,Al)Si2O6
Augite(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6]
ClinoenstatiteMgSiO3
ClinoferrosiliteFe2+SiO3
DiopsideCaMgSi2O6
EsseneiteCaFe3+[AlSiO6]
HedenbergiteCaFe2+Si2O6
JadeiteNa(Al,Fe3+)Si2O6
Jervisite(Na,Ca,Fe2+)(Sc,Mg,Fe2+)Si2O6
JohannseniteCaMn2+Si2O6
KanoiteMn2+(Mg,Mn2+)Si2O6
KosmochlorNaCrSi2O6
KushiroiteCaAl[AlSiO6]
NamansiliteNaMn3+Si2O6
NatalyiteNaV3+Si2O6
Omphacite(Ca,Na)(Mg,Al)Si2O6
PetedunniteCa(Zn,Mn2+,Mg,Fe2+)Si2O6
Pigeonite(Mg,Fe2+,Ca)(Mg,Fe2+)Si2O6
SpodumeneLiAlSi2O6
9.DA.05Donpeacorite(Mn2+,Mg)Mg[SiO3]2
9.DA.05EnstatiteMgSiO3
9.DA.05FerrosiliteFeSiO3
9.DA.10ClinoenstatiteMgSiO3
9.DA.10ClinoferrosiliteFe2+SiO3
9.DA.10KanoiteMn2+(Mg,Mn2+)Si2O6
9.DA.10Pigeonite(Mg,Fe2+,Ca)(Mg,Fe2+)Si2O6
9.DA.15Augite(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6]
9.DA.15DiopsideCaMgSi2O6
9.DA.15EsseneiteCaFe3+[AlSiO6]
9.DA.15HedenbergiteCaFe2+Si2O6
9.DA.15JohannseniteCaMn2+Si2O6
9.DA.15PetedunniteCa(Zn,Mn2+,Mg,Fe2+)Si2O6
9.DA.15DavisiteCaScAlSiO6
9.DA.15KushiroiteCaAl[AlSiO6]
9.DA.15GrossmaniteCaTi3+ AlSiO6
9.DA.20Aegirine-augite(Na,Ca)(Fe3+,Fe2+,Mg,Al)Si2O6
9.DA.20Omphacite(Ca,Na)(Mg,Al)Si2O6
9.DA.25JadeiteNa(Al,Fe3+)Si2O6
9.DA.25Jervisite(Na,Ca,Fe2+)(Sc,Mg,Fe2+)Si2O6
9.DA.25KosmochlorNaCrSi2O6
9.DA.25NamansiliteNaMn3+Si2O6
9.DA.25NatalyiteNaV3+Si2O6
9.DA.30SpodumeneLiAlSi2O6
14.20.1EmeleusiteLi2Na4Fe2Si12O30
14.20.4WilkinsoniteNa2Fe42+Fe23+(Si6O18)O2
14.20.5TuperssuatsiaiteNa2Fe3Si8O20(OH)2 · 4H2O
14.20.6Riebeckite◻[Na2][Fe32+Fe23+]Si8O22(OH)2
14.20.7 Ferri-annite
14.20.8Fenaksite(K,Na)4(Fe,Mn)2(Si4O10)2(OH,F)
14.20.9Montdorite(K,Na)2(Fe2+,Mn2+,Mg)5(Si4O10)2(OH,F)4

Other Names for Aegirine

Name in Other Languages:

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 Aegirine

Reference List:
Ström, P. (1821) Undersökning af ett nytt Fossil. Kongliga Vetenskaps-Academiens Handlingar: 160-163. [Acmite]

Berzelius, J. (1821) Tillägg til föregående Afhandling. Kongliga Vetenskaps-Academiens Handlingar: 163-166. [Acmite]

Berzelius, J. (1835) Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde (von Leonard und Bonn): 1835: 184-185. [Aegirine, Esmark]

(1876) Neues Jahrbuch für Mineralogie: 175: 352-358.

Anonymous (1947) Til opprinnelsen av mineralnavnet ”Ægirin”. Norsk Geologisk Tidsskrift: 26: 144-145.

Clark, J.R., Appleman, D.E., Papike, J.J. (1969) Crystal-chemical characterization of clinopyroxenes based on eight new structure refinements. MSA Special Paper: 2: 31-50.

Cameron, M., Shigeho, S., Prewitt, C.T., Papike, J.J. (1973) High temperature crystal chemistry of acmite, diopside, hedenbergite, jadeite, spodumene and ureyite. American Mineralogist: 58: 594-618.

Morimoto, N., Fabries, J., Ferguson, A.K., Ginzburg, I.V., Ross, M., Seifert, F.A., Zussman, J., Aoki, K., Gottardi, G. (1988) Nomenclature of Pyroxenes. American Mineralogist: 73: 1123-1133.

Raade, G. (2010) Chemical composition of acmite/aegirine intergrowths from Rundemyr, Eiker. Norsk Bergverksmuseum Skrift: 43: 29-34.

Ribeiro Da Costa, I., Rodrigues, C.R., Barriga, F.J.A.S., Rona, P.A., Nunes, C.D., Vaz, P.D. (2014): Colourless aegirine in metamorphic rocks from Bayan Obo (Inner Mongolia): lack of charge transfer transitions as possible explanation. European Journal of Mineralogy: 25(6): 987-993.

Internet Links for Aegirine

Specimens:
The following Aegirine specimens are currently listed for sale on minfind.com.

Localities for Aegirine

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.
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