Allanite-(Y)

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.
See more at Wikipedia.org...

General Information:
 Chemical Formula:
(Y,Ce,Ca)2(Al,Fe+++)3(SiO4)3(OH)
 Composition:
(Molecular Weight = 598.63 gm)
Calcium 2.01 % Ca
Cerium 14.04 % Ce
Yttrium 17.82 % Y 
Aluminum 10.14 % Al
Iron 7.00 % Fe
Silicon 14.07 % Si
Hydrogen 0.17 % H 
Oxygen 34.74 % O 
 Empirical Formula:
Y1.2Ce0.6Ca0.3Al2.25Fe3+0.75(SiO4)3(OH)
 IMA Status:
Approved IMA 1987
 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
More details...