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Formula: BaY6B6Si3O24F2
Nesosilicate (insular SiO4 groups), borosilicate,
barium- and yttrium-
bearing mineral
Crystal System: Trigonal
Specific gravity: 4.407 measured, 4.43 calculated
Hardness: 6 to 6½
Streak:
Colour: Greenish brown
Environments
Localities
At Lille Arøya, Larvik, Vestfold, Norway, cappelenite-(Y) occurs in a small vein in
nepheline syenite
pegmatite, associated with
wöhlerite, rosenbuschite,
thorite, catapleiite,
låvenite, nepheline and
sodalite
(HOM).
At the type locality, Natrolittodden, Vesle Arøya, Larvik, Vestfold, Norway, only a few specimens of
yellow-brown cappelenite-(Y) have been found in a small
nepheline syenite
pegmatite.
Cappelenite-(Y) is completely metamict, but is reconstituted by heating to 700oC. It is one of
very few yttrium-bearing minerals from the
nepheline syenite
pegmatites of the Oslo region (others include
fergusonite-(Y),
xenotime-(Y),
tritomite-(Y),
hingganite-(Y),
allanite-(Y) and
kainosite-(Y))
(JWW p162, p152).
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