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Formula: NaY(CO3)F2
Anhydrous carbonate, yttrium-bearing mineral
Crystal system: Orthorhombic
Specific gravity: 3.58 measured, 3.46 calculated
Hardness: 4
Streak: White
Colour: Colourless to pale beige
Luminescence: Does not fluoresce under UV
Environments
Localities
The type locality is the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec,
Canada. Mont Saint-Hilaire is an alkaline intusive complex. Horváthite-(Y) is a very rare mineral; specimens
were collected from a large pegmatite dike in the
nepheline syenite intrusive unit. The portion of the
pegmatite in which horváthite-(Y) was found is
quite altered; many of the minerals with horváthite-(Y) inclusions are etched and corroded.
Horváthite-(Y) is associated with microcline,
aegirine, dawsonite,
rhodochrosite, sodalite,
natrolite, albite,
serandite, siderite,
tainiolite, catapleiite,
astrophyllite,
genthelvite, and a
franconite group mineral. In another part of the same
pegmatite dike, horváthite-(Y) is also associated
with adamsite-(Y) (previously UK96), an alteration product of
adamsite-(Y), sphalerite,
rhodochrosite and
microcline.
Horváthite-(Y) has two distinct habits: (1) stacks of plates, measuring approximately 1 X 1 X 0.25
mm3, and (2) blocky aggregates of radiating crysals 1 to 5 mm across wilh individual, striated
prismatic crystals up to 1 mm long. The aggregates are commonly "wagon-wheel" or cylindrical in habit
(CM 35.3.743-749).
Horváthite-(Y) from the Poudrette Quarry -
Image
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