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Aegirine
A valid IMA mineral species
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Colour:
Dark green to greenish black, reddish brown, black
Lustre:
Vitreous
Hardness:
6
Specific Gravity:
3.5 - 3.6
Crystal System:
Monoclinic
Member of:
Name:
First described asacmit by P. H. Ström (1821) fromRundemyr, 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 namewernerin, after the German geologist, Abraham Gottlob Werner. But Berzelius (1821), who analysed the mineral, named itachmit 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 onLåven, Langesundsfjorden, Norway which was described and given the nameaegirine, 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).
Later, in 1834, the priest and mineralogist Hans Morten Thrane Esmark found a new mineral onLåven, Langesundsfjorden, Norway which was described and given the nameaegirine, 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 et al., 1988).
However, at the Rundemyr locality, the TL, both brownish and green-black varieties occur as intergrowths. Raade (2010) 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.
The deep colour typical for most aegirines is thought 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 forgemological information about Aegirine.
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 et al., 1988).
However, at the Rundemyr locality, the TL, both brownish and green-black varieties occur as intergrowths. Raade (2010) 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.
The deep colour typical for most aegirines is thought 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 forgemological information about Aegirine.
![NaFe3+Si2O6](#"/photo-250039.html"><img src="/image.pl?url=https%3a%2f%2fwww.mindat.org%2fimagecache%2f4e%2fff%2f05392110017271920945173.jpg&f=jpg&w=240" alt="05392110017271920945173.jpg" /></a><div><b>Ægir</b></div></div></div><div><div><span>Formula:</span><div class=){kind=link}