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Formula: Na2ZrSi3O9.2H2O
Cyclosilicate (ring silicate), gaidonnayite group, orthorhombic
paramorph of monoclinic
catapleiite
Crystal System: Orthorhombic
Specific gravity: 2.67 measured, 2.70 calculated
Hardness: 5
Streak: White
Colour: Colourless, may be pale yellow, pale brown to brown, pale grey, grey-green.
Solubility: Gelatises in acids Dana
Common impurities: Ti,Nb,Ca,K
Environments:
Gaidonnayite occurs in altered pegmatites and miarolitic cavites in
nepheline syenite (Webmin).
At the type locality, the Poudrette quarry, Mont Saint-Hilaire, Montérégie, Québec, Canada, gaidonnayite occurs in altered
pegmatite dikes in an intrusive alkaline
gabbro-syenite complex, and rarely
in miarolytic cavities in nepheline syenite and breccia cavities; also
in an igneous sill in limestone (Dana, HOM). Associated minerals include
siderite, analcime,
hilairite, aegirine,
calcite, albite,
catapleiite, zircon,
pyrochlore, ancylite and
burbankite (HOM).
At the Kipawa syenite complex, Temiscamingue county, Quebec, Canada,
gaidonnayite occurs in eudialyte-rich pegmatite lenses as a late-stage alteration
product of vlasovite (Dana), associated with
vlasovite, gittinsite and
apophyllite (HOM).
At Narssarssuk, Greenland, Denmark, gaidonnayite occurs in a vein of aegirine
syenite (Dana), associated with
natrolite, aegirine,
albite and siderite (HOM, Dana).
At Bronnebukta, Norway, gaidonnayite occurs in a nepheline syenite
pegmatite (Dana).
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