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Formula: (K,Na,☐)12Nb8(Si4O12)4O8.12-16H2O
Cyclosilicate (ring silicate), vuoriyarvite group,
labuntsovite supergroup,
niobium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.95 measured, 3.02 calculated
Hardness: 4½
Streak: White
Colour: White
Luminescence: Not fluorescent
Solubility: Insoluble in dilute hydrochloric and sulphuric acids
Common impurities: Na
Environments
Carbonatites
Hydrothermal environments
Localities
At the type locality, the Vuoriyarvi alkaline-ultrabasic massif, Northern Karelia, Murmansk Oblast, Russia,
vuoriyarvite-(K) occurs as dull white tabular crystals up to 3 mm long in veins of
dolomite-calcite
carbonatite that cut
pyroxenites. It formed from hydrothermal alteration of
pyrochlore, and is associated with
calcite, dolomite,
strontianite, ewaldite,
serpentine, apatite,
pyrrhotite, pyrite,
chalcopyrite and sphalerite
(AM 83.1347-1352).
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