Allanite

sorosilicate

epidote

Formulae:
allanite-(Ce) CaCe(Al2Fe2+)[Si2O7][SiO4]O(OH)
allanite-(La) CaLa(Al2Fe2+)[Si2O7][SiO4]O(OH)
allanite-(Nd) CaNd(Al2Fe2+)[Si2O7][SiO4]O(OH)
allanite-(Y) CaY(Al2Fe2+)[Si2O7][SiO4]O(OH)
Sorosilicates, epidote group and form a complete solid solution series with it.
Specific gravity: allanite-(Ce) 3.4 to 4.2; allanite-(La) 3.69 to 4.02
Hardness: allanite-(Ce) 5 to 6½ allanite-(La) 5 to 5½ allanite-(Y) 6
Streak: allanite-(Ce) light brown
Colour: allanite-(Ce) light brown to black
Solubility: allanite-(Ce) gelatinises with hydrochloric acid Dana
Environments

Plutonic igneous environments
Pegmatites
Metamorphic environments

The allanite minerals are sorosilicates containing the rare earth elements cerium Ce, lanthanum La, neodymium Nd and yttrium Y, and are often metamict. Allanites are a common accessory mineral in granite, granodiorite, monzonite, syenite, and granitic pegmatite. They are also found in diorite and gabbro, as phenocrysts in acidic volcanic rocks, and in a number of metamorphic rock types (R&M 86.5.450).

At Pacoima Canyon, Los Angeles County, California, USA, allanite occurs with zircon and apatite in a pegmatite (AM 56.447).

Allanite-(Ce)

Allanite-(Ce) is an accessory mineral in some granites and granite pegmatites and syenites, and more rarely in gabbroic pegmatites; it occurs rarely in schist, gneiss and some contact metamorphosed limestones, and it can be a detrital mineral (Dana, HOM). Associated minerals include epidote, muscovite and fluorite (HOM, Mindat).

The type locality for allanite-(Ce) is Qáqarssuatsiaq, Aluk Island, Kujalleq, Greenland, Denmark.

At the Trimouns quarry, Ariège, France, allanite-(Ce) is found in dolomite and talc, and may be associated with bastnäsite, synchysite, parisite, quartz, calcite, and very rarely hingganite (R&M 35.3.232, R&M 86.5.451).

At the Bastnas mines, Vastmanland, Sweden, allanite-(Ce) occurs within amphibole skarn and as compact masses with cerite. Associated minerals include chalcopyrite, bismuthinite, bastnäsite and rarely linnaeite (R&M 35.3.193-194).

At the Tiro Estrella mine, Lincoln County, New Mexico, USA, allanite-(Ce) occurs in quartz veins with feldspar.

At Power's Farm, Pierrepont, St. Lawrence county, New York, USA, allanite-(Ce) occurs as a late-stage mineral associated with microcline, quartz, and chamosite (R&M 85.2.162).

At the danburite occurrence near Russell, St. Lawrence county, New York, USA, allanite-(Ce) forms crystals on tremolite (R&M 90.3.217).

At the Selleck Road Locality, West Pierrepont, St. Lawrence county, New York, USA, allanite-(Ce), or a closely related species, occurs on the surfaces of microcline crystals (R&M 91.2.121).

In New York city, New York, USA, an allanite-(Ce) crystal has been found at the southeast corner of 56th and Broadway embedded in albite pegmatite, and another allanite-(Ce) crystal has been found embedded in quartz from the Brooklyn-Battery Tunnel (R&M 84.3.221-222).

Allanite-(La)

At Serifos island, Cyclades, Greece, allanite-(La) occurs in skarn (Dana).

At the type locality, the Buca della Vena Mine, Stazzema, Lucca Province, Tuscany, Italy allanite-(La) occurs in baryte veins cutting a dolomitic metamorphosed limestone (Mindat, R&M 86.5.451, Webmin, HOM), associated with calcite and baryte (HOM).

At the Nueva Vizcaya mine, Badajoz, Spain, crystals of allanite-(La) occur in skarn associated with magnetite, actinolite, albite, epidote, and titanite (R&M 86.5.451). Although allanite-(La) is very rare generally, it is relatively common on a particular part of the dump at the Nueva Vizcaya mine, embedded in calcite (Min Rec 33-6.491-494).

Allanite-(Nd)

At the type locality, the Åskagen Quarry, Filipstad, Värmland, Sweden, allanite-(Nd) occurs as aggregates within altered thalénite-(Y). Associated minerals include iimoriite-(Y), keiviite-(Y), allanite-(Y) and tengerite-(Y) (AM 97.983-988).
Common impuritiesin allanite-(Nd): Al,Ca,Ce,Fe,La,Mg,Mn,Pr,Sm,Ti

Allanite-(Y)

Allanite-(Y) was originally described from the Zaaiplaats tin mine, Potgietersrust district, Transvaal, South Africa. It occurs in an explosion breccia in a cassiterite-bearing pipe in granite, in hydrothermally altered arkoses, and in granitic pegmatite (Dana).

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