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Formula: K2NaFe2+7Ti2Si8O26(OH)4F
Inosilicate (chain silicate)
Forms a series with kupletskite
Crystal System: Triclinic
Specific gravity: 3.2 to 3.4 measured
Hardness: 3
Streak: Golden
Colour: Bronze-yellow, golden yellow, brown to reddish brown
Common impurities: Nb,Ta,Zr,Al,Mg,Ca
Environments:
Plutonic igneous environments
Pegmatites
Metamorphic environments
Astrophyllite is found in nepheline syenite,
syenite
pegmatites, alkaline
granite and
nepheline syenite
gneiss.
(Dana, HOM).
Associated minerals include albite, aegirine,
arfvedsonite, nepheline,
natrolite, zircon,
biotite,
leucophanite, eudialyte,
catapleiite, djerfisherite,
rasvumite, delhayelite and
kupletskite
(HOM Dana).
Localities
At the the Verkhnee Espe deposit, Kazakhstan, astrophyllite occurs on
granite with
cámaraite, bafertisite,
jinshajiangite, fluoro-leakeite
and aegirine
(R&M 86-2.165).
At the type locality, Låven, Vestfold, Norway, astrophyllite occurs in a
nepheline syenite
pegmatite
(Mindat).
At the Zagi mountain, Pakistan, astrophyllite is found as inclusions in quartz,
microcline, xenotime and
bastnäsite, but it has not been observed as free-standing crystals
(MinRec 35.3.212).
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