Yttrialite-(Y)

sorosilicate

thortveitite

Formula: Y2S2O7
Sorosilicate, usually metamict, thortveitite group
Specific gravity: 4.31 to 4.56
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

Pegmatites

Yttrialite is a late-stage yttrium-bearing mineral in some rare-earth-bearing pegmatites, associated with gadolinite-(Y), tengerite-(Y), thalénite, thortveitite, britholite-(Y), fergusonite, xenotime, allanite, microcline, albite, quartz, biotite, zircon, magnetite, spessartine and fluorite (HOM, Webmin, Dana).

Yttrialite alters to Y-carbonates, tengerite and others (Dana).

The type locality is Baringer Hill, Bluffton, Llano county, Texas, USA.

At the Rode Ranch pegmatite, Llano county, Texas, USA, Yttrialite occurs with thin laminations of tengerite (AM 58.545).

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