Watatsumiite is the variety with vanadium replacing the titanium in the formula.

[3] It is also found within natrolite veins in glaucophane schist within serpentinite in San Benito County, California, US.

It also occurs in Mont Saint-Hilaire, Quebec[5] and in the Kola Peninsula of Russia.

[2] The mineral is named for Neptune, Roman god of the sea because of its association with aegirine from Àgir, the Scandinavian sea-god.

[3] The Gemological Institute of America (GIA) identified an 11.78-carat faceted specimen as neptunite based on Raman spectroscopy.