Allanite group minerals include:
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)
ferriallanite-(Ce):
CaCe(Fe3+AlFe2+)[Si2O7][SiO4]O(OH)
ferriandrosite-(Ce):
MnCe(Fe3+AlMn2+)(Si2O7)(SiO4)O(OH)
Sorosilicates (Si2O7 groups),
epidote supergroup
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).
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