aegirine

a pyroxene mineral, sodium and iron silicate (NaFe+3Si2O6), that is commonly found in alkaline igneous rocks, particularly in syenites and syenite ... [2 related articles]
Found on http://www.britannica.com/eb/a-z/a/22

Aegirine

Aegirine is a member of the clinopyroxene group of inosilicates. Aegirine is the sodium endmember of the aegirine-augite series. Aegirine has the chemical formula NaFeSi2O6 in which the iron is present as Fe3+. In the aegirine-augite series the sodium is variably replaced by calcium with iron(II) and magnesium replacing the iron(III) to balance th...
Found on http://en.wikipedia.org/wiki/Aegirine
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