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Download hereGENERAL DESCRIPTION
Allanite-(Ce) is a complex hydrated silicate of calcium, yttrium, aluminium and of iron, also containing rare earths. The rare earths that one can be found in the allanite are generally lanthanum (La) and cerium-(Ce). Some others allanites are rich in yttrium-(Y).
The cerium-bearing species is most widespread of the 3 species of allanites known (allanite-(La) and allanite-(Y)). Allanites belong to the group of epidotes. It is a species which one finds in the granites, the granitic pegmatites, in certain syenites and some sedimentary rocks.
The allanite-(Ce) is presented in the form of tabular or prismatic crystals. The most important deposits are the Eifel Mounts in Germany, he tpegmatites of the quarry of Baringer Hill in Texas where samples of allanite of more than 135 kg were discovered.
In France, it was discovered as gemmeous prismatic crystals measuring approximately 2,5 cm in the quarry of Trimouns in Ariège. Other French deposits are: massif of the Lauzière in Savoie and that of the Mont Blanc in Haute-Savoie.
The type of this species (originating in Qáqarssuatsiaq, close of Aluk in the south Greenland) is kept at the Natural History Museum of London and the University of Copenhagen in Denmark.
HISTORY : Species dedicated to Thomas Allan (1777-1833), Scottish mineralogist who discovered the mineral
Species first described in 1810 by Thomas Thomson (1773-1852), Scottish mineralogist and chemist
Type-locality: Iglorsoit, Groënland
ANCIENT NAME : Orthite
CHEMICAL FORMULA : (Ca,Ce)2 (Al,Fe2+,Fe3+)3 (SiO4) (Si2O7) O (OH)
CRYSTAL SYSTEM : Monoclinic
COLOR : Brown to black
DIAPHANIETY : Translucent to opaque
LUSTER : Vitreous to resineous
STREAK : Gray
MORPHOLOGIE : Tabular crystals, prismatic to acicular
HARDNESS : 5,5-6,0
CHEMICAL CLASS: 4,11
DENSITY : VIII - Silicates
GROUP : Epidote
STRUNZ CLASS BEFORE 2001 : 8/C.23-80
STRUNZ CLASS AFTER 2001 : 9.BG.05
