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Formula: Na6(Na☐)Ba2Ti2Nb2(Si2O7)4(PO4)2O4(OH)2F2
Sorosilicate (Si2O7 groups),
lamprophyllite group,
barium, titanium and
niobium bearing mineral
Crystal System: Triclinic
Specific gravity: 3.47 to 3.5 measured, 3.49 calculated
Hardness: 3½ to 4
Streak: White
Colour: Pale yellow
Solubility: Decomposed by cold 5% hydrochloric or nitric acid, depositing silica gel (AM 61.338)
Common impurities: Zr,Al,Fe,Mn,Mg,Ca,Sr,Li,K,Rb
Environments
Pegmatites
Hydrothermal environments
Bornemanite occurs as a late hydrothermal mineral in the natrolite
zone of alkalic pegmatites in a differentiated alkalic massif.
Associated minerals include natrolite and
lomonosovite
(Webmin, HOM).
Localities
At the Shkatulka pegmatite, Umbozero mine, Alluaiv Mountain, Lovozersky District, Murmansk Oblast, Russia,
bornemanite occurs as spherulites associated with lomonosovite
and other minerals
(CM 39.1665-1673).
At the Sirenevaya pegmatite, Umbozero mine, Alluaiv Mountain, Lovozersky District, Murmansk Oblast, Russia,
bornemanite occurs as spherulites associated with lomonosovite
and other minerals, and occasionally it is seen also to replace
lomonosovite
(CM 39.1665-1673).
At the type locality, the Yubileinaya pegmatite, Karnasurt Mountain, Lovozersky District, Murmansk Oblast, Russia,
bornemanite occurs yellow platy aggregrates, to 1 cm, of fine leaflets along cleavages and on the surface of
lomonosovite and in natrolite,
in the natrolite zone of the
pegmatite; it occasionally completely replaces
lomonosovite
(AM 61.338, CM 39.1665-1673).
At the Palitra pegmatite, Karnasurt mine, Kedykverpakhk Mountain, Lovozersky District, Murmansk Oblast, Russia,
bornemanite was found in a late-stage assemblage as yellow spheroids to 2 mm in diameter. It commonly forms
overgrowths on lomonosovite and in some cases replaces it. Occasionally
it is found intergrown in villiaumite and
natrosilite
(Minrec 36.5.403).
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