A nice single brown crystal aggregate of the very rare Mg nitrate mineral nitromagnesite from a locality in France: Baume-les-Messieurs, Jura, Bourgogne-Franche-Comté, France. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Nitromagnesite
Nitromagnesite is an IMA-recognized mineral species in the nitrate class, with the chemical formula Mg(NO₃)₂·6H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: specific gravity 1.46–1.58; Vitreous luster; optically biaxial.
IMA symbol Nmgs, grandfathered status — known before the IMA’s founding, named in 1783.
A rare cave deposit in humidities up to 78%, typically formed as a leachate of bat guano; may be a component of mixed salts.
It is found associated with Nitrocalcite.
The name refers to NITROgen and MAGNESium in the composition.