Xenotime

phosphate

ytterbium

Formulae:
xenotime-(Y): Y(PO4)
xenotime-(Yb): Yb(PO4)
Phosphates. Xenotime-(Y) forms a series with xenotime-(Yb) and with chernovite-(Y). Zircon is an epitaxial mineral (Mindat)
Data for xenotime-(Y), which is by far the more common mineral
Specific gravity: 4.4 to 5.1
Hardness: 4 to 5
Streak: Pale brown, yellowish or reddish, white
Colour: Yellowish brown, reddish brown, light red, flesh-red, light green, grey, greyish white, wine-yellow. Colourless to very light yellowish green, yellow or yellowish brown in transmitted light (Mindat)
Solubility: Very lightly attacked by acids
Environments:

Igneous environments
Pegmatites
Placer deposits

Xenotime is a rare phosphate of yttrim or ytterbium that occurs as an accessory mineral in both acid and alkaline rocks, and their associated pegmatites; it also occurs in mica, gneiss and Alpine veins, and is a common detrital mineral in placers (HOM, Webmin, Dana). Associated minerals include zircon, monazite, rutile, anatase, brookite, hematite, ilmenite, gadolinite, allanite, apatite, yttrotantalite, magnetite, sillimanite, feldspar and thorite (HOM, Dana, Mindat) and occasionally fergusonite and columbite - tantalite (Dana).

At Llallagua, Bolivia, xenotime has been found on monazite (MinRec 37.2.160). At the type locality for xenotime-(Yb), Shatford Lake pegmatite, Lac-du-Bonnet area, Manitoba, Canada, Xenotime-(Yb) is found in albite in a granitic pegmatite (Webmin).

At Saint-Pierre-de-Broughton, Quebec, Canada, xenotime-(Y) is an exceedingly rare accessory mineral found in small cavities in albite schist hosting anatase and brookite bearing Alpine fissures. It's only associate here is chamosite (R&M 85.6.508-509).

At Trimouns quarry, France, xenotime is found, rarely, in small vugs in crystallised dolomite and calcite (MinRec 35.3.244).

At Erongo, Namibia, xenotime is associated with beryl variety aquamarine, fluorite and quartz. It has also been found on metazeunerite from the uranium pocket (MinRec 37.5.454).

In the river alluvium in the Grey River-Mawheraiti River area, North Westland, New Zealand, xenotime has been found as a minor constituent of an assemblage that includes zircon, ilmenite, spessartite - almandine, monazite, and tantalum-rich cassiterite (AM 32.141).

At the type locality, Hidra, Flekkefjord, Norway, xenotime was found in a granite pegmatite associated with gadolinite, polycrase - euxenite, allanite, zircon, yttrotantalite and thorite (Dana).

At the Zagi mountain, Pakistan, xenotime, quartz and microcline have been found together on a specimen, with all three minerals having inclusions of astrophyllite (MinRec 35.3.219-220 ).

At Cheyenne Canyon, Pikes Peak, El Paso county, Colorado, USA, xenotime has been found with fluorcerite and bastnäsite (Dana).

In the Manhattan schist, New York City, USA, xenotime and monazite crystals have been found in a vein of coarse-grained grey granite running through the local mica schist, and also in a pegmatite vein in the schist (R&M 84.3.236-237 )

At Polk, McDowell, Burke county, North Carolina, USA, xenotime occurs as a detrital mineral in placer gold deposits (Dana).

In the Wassau Complex pegmatites, Marathon county, Wisconsin, USA, xenotime-(Y) has been found in a greisen assemblage associated with cassiterite, ferberite / hübnerite and topaz (R&M 88-4.361-362).

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