A crystal of aegirine from the type locality, the island of Låven in Langesundfjorden, was studied by electron microprobe analysis, X ray diffraction, Mössbauer and infrared spectroscopy, and optical microscopy. In spite of its apparently homogeneous appearance, the crystal contained minor inclusions of other minerals, especially biotite and sodalite. Microprobe analyses and Mössbauer spectroscopy showed that the crystal classifies as an aegirine, consisting of 78 % end-member aegirine with lesser proportions of the “quadrilateral” Ca Fe Mg pyroxenes and jadeite.