Kostylevite

kostylevite

umbite

wadeite

eudialyte

Images

Formula: K₂ZrSi₃O₉.H₂O
Valence: K₂Zr⁴⁺Si₃O₉.H₂O
Cyclosilicate (ring silicate), zirconium-bearing mineral, monoclinic paramorph of orthorhombic umbite
Crystal System: Monoclinic
Specific gravity: 2.74 measured, 2.79 calculated
Hardness: 5
Streak: White
Colour: Colourless
Solubility: Decomposed by cold 10% hydrochloric acid
Common impurities: Ti,Hf,Fe
Environments

Pegmatites

Localities

At the type locality, the Vuonnemiok River Valley, Murmansk Oblast, Russia, kostylevite occurs in an alkalic pegmatite, intergrown with umbite and wadeite, and associated with eudialyte, K-feldspar and aegirine (AM 69.810-815).


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