Allanite-(La)

Allanite is a sorosilicate group of minerals within the broader epidote group that contain a significant amount of rare earth elements. It has the general formula Ca(Ce,La,Y,Ca)Al2(Fe2+,Fe3+)(SiO4)(Si2O7)O(OH). The International Mineralogical Association lists three minerals in the allanite group, each recognized as a unique mineral: allanite-Ce, allanite-La and allanite-Y, depending on the dominant rare earth present.
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General Information:
 Chemical Formula:
Ca(La,Ce)(Fe++,Mn++)(Al,Fe+++)2(SiO4)(Si2O7)O(OH)
 Composition:
(Molecular Weight = 596.56 gm)
Calcium 6.72 % Ca
Lanthanum 17.46 % La
Cerium 5.87 % Ce
Manganese 2.30 % Mn
Aluminum 6.78 % Al
Iron 11.70 % Fe
Silicon 14.12 % Si
Hydrogen 0.17 % H 
Oxygen 34.87 % O 
 Empirical Formula:
CaLa0.75Ce0.25Fe2+0.75Mn2+0.25Al1.5Fe3+0.5(SiO4)(Si2O7)O(OH)
 IMA Status:
Not IMA Approved
 Locality:
TL: Russia, Karelia
 Name Origin:
Named after the Scottish mineralogist, T. Allan (1777-1833).
Physical Properties:
 Cleavage:
[001] Imperfect, [100] Imperfect
 Color:
brown or black.
 Density:
3.3 - 4.2, Average = 3.75
 Diaphaniety:
Translucent to opaque
 Habits:
Massive - Granular - Common texture observed in granite and other igneous rock., Disseminated - Occurs in small, distinct particles dispersed in matrix.,
 Hardness:
5.5 - Knife Blade
 Luminescence:
None.
 Luster:
Vitreous - Greasy
 Streak:
grayish brown
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