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Formula: Ca12Al14O32[(H2O)4F2]
Oxide, mayenite supergroup
Crystal System: Isometric
Hardness: 5½ to 6
Streak: White
Colour: Colourless
Luminescence: Not fluorescent under UV
Common impurities: Fe(III),Si,OH
Environments
Metamorphic environments
Hydrothermal environments
Localities
At the type locality, the Hatrurim Basin, Tamar Regional Council, Southern District, Israel,
fluorkyuygenite is a major constituent of larnite pyrometamorphic
rocks. Mineral associations
of holotype fluorkyuygenite include larnite,
shulamitite,
chromium-bearing minerals of the
spinel – magnesioferrite
series, ye’elimite,
fluorapatite –
fluorellestadite,
periclase,
brownmillerite
and oldhamite as well as the retrograde phases
portlandite, hematite,
hillebrandite, afwillite,
foshagite, ettringite,
katoite and hydrocalumite.
Fluorkyuygenite crystals, usually < 20 μm in size, are colourless, in places with greenish or yellowish
tint, transparent with a vitreous lustre.
Fluorkyuygenite crystallised initially as fluormayenite,
which later was altered under the influence of water vapour-enriched gases during a combustion process
(EJM 27.123-136).
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