Aegirine
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| Aegirine | |
|---|---|
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| General | |
| Category | Silicate mineral, pyroxene |
| Formula | Page Module:Chem2/styles.css has no content.NaFe3+[Si2O6] |
| IMA symbol | Aeg[1] |
| Strunz classification | 9.DA.25 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/c |
| Unit cell | a = 9.658, b = 8.795 c = 5.294 [Å], β = 107.42°; Z = 4 |
| Identification | |
| Formula mass | 231.00 g/mol |
| Color | Dark Green, Greenish Black |
| Crystal habit | Prismatic crystals may be in sprays of acicular crystals, fibrous, in radial concretions |
| Twinning | Simple and lamellar twinning common on {100} |
| Cleavage | Good on {110}, (110) ^ (110) ≈87°; parting on {100} |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 6 |
| Luster | Vitreous to slightly resinous |
| Streak | Yellowish-grey |
| Diaphaneity | Translucent to opaque |
| Specific gravity | 3.50–3.60 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.720 – 1.778 nβ = 1.740 – 1.819 nγ = 1.757 – 1.839 |
| Birefringence | δ = 0.037 – 0.061 |
| Pleochroism | X = emerald green, deep green; Y = grass-green, deep green, yellow; Z = brownish green, green, yellowish brown, yellow |
| 2V angle | Measured: 60° to 90°, Calculated: 68° to 84° |
| Dispersion | moderate to strong r > v |
| References | [2][3][4][5] |
Aegirine is a mineral. It is a member of the clinopyroxene group of inosilicate minerals. Acmite is a fibrous green-colored variety of aegirine, with the name also used as a synonym. It was first described in 1821, in Kongsberg, Norway.
Etymology
The name aegirine is derived from Ægir , a Norse mythological figure (god of the sea), as the mineral was first described from Norway.[2][3]
A synonym for the mineral is acmite (from Greek ἀκμή "point, edge") in reference to the typical pointed crystals.[6]
Chemistry and description
Aegirine is the sodium endmember of the aegirine–augite series.[citation needed]
It has the chemical formula NaFeSi2O6, in which the iron is present as the ion Fe3+. In the aegirine–augite series, the sodium is variably replaced by calcium with iron(II) and magnesium replacing the iron(III) to balance the charge. Aluminum also substitutes for the iron(III). Acmite is a fibrous green-colored variety.[citation needed]
Aegirine occurs as dark green monoclinic prismatic crystals.[3] It has a glassy luster and perfect cleavage, "in two directions at near 90 degree angles".[7] It is described on Mindat.org as "slightly resinous", with its colour "dark green to greenish black, reddish brown, [or] black" Its Mohs hardness is 6 and its specific gravity is between 3.5 and 3.6.[3][4]
Associated minerals include augite, nepheline, andradite, baryte, quartz, spessartine, riebeckite, biotite, sodalite, and albite.[7]
Occurrence
The acmite variety was first described in 1821, at Kongsberg, Norway,[8] and the aegirine variety in 1835 for an occurrence in Rundemyr, Øvre Eiker, Buskerud, Norway.[3]
This mineral commonly occurs in alkalic igneous rocks, nepheline syenites, carbonatites, and pegmatites. It also appears in regionally metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites. It may occur as an authigenic mineral in shales and marls. It occurs in association with potassic feldspar, nepheline, riebeckite, arfvedsonite, aenigmatite, astrophyllite, catapleiite, eudialyte, serandite, and apophyllite.[2]
Major localities include Mont Saint-Hilaire, Quebec, Canada; Kongsberg, Norway; Narsarssuk, Greenland; Kola Peninsula, Russia; Magnet Cove, Arkansas, US; Kenya; Scotland, and Nigeria.[7]
Aegirine also occurs in the syenite at the Bowral quarries in New South Wales, Australia, as described in a 1906 paper by geologist and later Antarctic explorer Douglas Mawson.[9][10]
Uses
Aegirine is sometimes used as a gemstone.[11]
See also
References
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- ^ Page Module:Citation/CS1/styles.css has no content.Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b c Page Module:Citation/CS1/styles.css has no content."Aegirine". Handbook of Mineralogy (PDF) (version 1.2 ed.). Mineral Data Publishing. 2001.
- ^ a b c d e Page Module:Citation/CS1/styles.css has no content."Aegirine". Mindat.org. Retrieved 9 August 2025.
- ^ a b Page Module:Citation/CS1/styles.css has no content."Aegirine Mineral Data". Mineralogy Database. Retrieved 9 August 2025.
- ^ Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Template:ISBN (via Internet Archive
- ^ Script error: No such module "template wrapper".
- ^ a b c Page Module:Citation/CS1/styles.css has no content."AEGIRINE (Sodium Iron Silicate)". mineral.galleries.com. Archived from the original on 7 May 2005. Retrieved 9 August 2025.
- ^ Page Module:Citation/CS1/styles.css has no content.Dana, James Dwight (1855) [1837]. Manual of Mineralogy (7th ed.). Philadelphia, PA: Durrie & Peck.
- ^ Page Module:Citation/CS1/styles.css has no content.Jago, James B.; Pharaoh, Mark D. (2 January 2016). "Pre-Antarctic Mawson in South Australia and western New South Wales". Transactions of the Royal Society of South Australia. 140 (1). Informa UK: 107–128. Bibcode:2016TRSAu.140..107J. doi:10.1080/03721426.2016.1149323. ISSN 0372-1426.
- ^ "The Minerals and Genesis of the Veins and Schlieren Traversing the Aegirine-Syenite in the Bowral Quarries". Proc. Linn. Soc. N.S.W., 381, pp. 580-607.
- ^ Page Module:Citation/CS1/styles.css has no content.Manutchehr-Danai, Mohsen (9 March 2013). Dictionary of Gems and Gemology. Springer Science & Business Media. p. 5. ISBN 978-3-662-04288-5.
External links
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