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Formula: Y2S2O7
Sorosilicate, (Si2O7 groups), usually metamict,
thortveitite group,
yttrium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 4.56 to 4.58 measured, 4.0 calculated
Hardness: 5½ to 6½
Streak: Greenish white or white
Colour: Orange-yellow (when altered), olive-green, greenish and brownish black, blackish or reddish brown
Solubility: Forms a gel in hot hydrochloric acid
Environments
Yttrialite-(Y) is a late-stage yttrium-bearing mineral in some rare-earth-bearing
pegmatites, associated with
gadolinite-(Y), tengerite-(Y),
thalénite-(Y), thortveitite,
britholite-(Y), fergusonite,
xenotime, allanite,
microcline, albite,
quartz, biotite,
zircon, magnetite,
spessartine and fluorite
(HOM, Webmin, Dana).
Localities
The type locality is Baringer Hill, Bluffton, Llano county, Texas, USA.
At the Rode Ranch pegmatite, Llano county, Texas, USA, yttrialite-(Y) occurs with thin laminations of
tengerite-(Y)
(AM 58.545).
Alteration
Yttrialite-(Y) alters to Y-carbonates, tengerite-(Y) and others
(Dana).
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