Inosilicate (chain silicate), neptunite group, and forms a series with it
Specific gravity: 3.23
Hardness: 5 to 6
Solubility: Insoluble in acids
Plutonic igneoous environments
Manganoneptunite is found as a late segregation mineral in almost all rock types, including
syenite and syenite
At Saint-Amable, Canada, manganoneptunite occurs in miarolitic cavities in a nepheline syenite sill (HOM).
At the type locality, Maly Mannepakhk Mountain, Khibiny Massif, Murmansk Oblast, Russia, manganoneptunite was found locally in the contact zone of the massif, associated with fibrous aegirine, natrolite, analcime, lamprophyllite, murmanite, lomonosovite, eudialyte, pectolite, villiaumite and sodalite (AM11.289-299, HOM), and also with lorenzenite (AM 12.96-97 )
At Point of Rocks, Colfax county, New Mexico, USA, manganoneptunite occurs in syenite and syenite pegmatite (Dana).
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