General Information:
Chemical Formula:(Y,Ce,Ca)2(Al,Fe+++)3(SiO4)3(OH)
Composition:(Molecular Weight = 598.63 gm)Calcium 2.01 %
CaCerium 14.04 %
CeYttrium 17.82 %
Y Aluminum 10.14 %
AlIron 7.00 %
FeSilicon 14.07 %
SiHydrogen 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
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