Mineral - Allanite-(Ce)
Allanite-(Ce)
Chemical Properties
Mineral Class
Silicates
Toxicity
radioactive
Formula
(CaCe)(AlAlFe²⁺)O[Si₂O₇][SiO₄](OH)
Unit Cell
a=8.93 b=5.77 c=10.16 β=115° Z=2
Physical Properties
Hardness
5.5 - 6
Streak
browngray
Density
Heavy (3,5-6)
Cleavage
Imperfect on (001), poor on (100) and (110)
Fracture
conchoidal,
uneven
Tenacity
Brittle
Optical Properties
Color
blackbrown
Birefringence
0.018 - 0.031
Luster
Vitreous,
Greasy
Transparency
translucent,
transparent,
opaque
Pleochroism
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
P2 1 /m (11)
Habit
granular, massive, prismatic, tabular
Formation
Igneous, in granitic-, syenitic-pegmatites. More rarely due to metamorphism
Paragenesis
Twinning
Polysynthetic twins on (100)
Rarity
Rather rare
Synonyms
Allanite-(Ce), Allanite
Composition
Elements
Mass
SiO₂
29.79
TiO₂
0.02
Al₂O₃
12.75
Y₂O₃
0.04
La₂O₃
7.20
Ce₂O₃
12.80
REE₂O₃
4.78
Fe₂O₃
10.64
FeO
9.02
MnO
0.85
MgO
0.64
CaO
10.10
H₂O
1.74
Zambia (Dana 1892)
Groups and Members
Epidote-Supergroup
Allanite-Group
Name and first discovery : Named after the Scottish mineralogist Thomas Allan (1777-1833), who examined the first allanite sample, which was found in Greenland in 1812 by the German mineralogist Carl Ludwig Giesecke (1761-1833).
Chemistry :
Synonyms : Bucklandite, Cerepidote, Cerorthite, Orthite
Varieties : Bagrationite, Chromium Allanite (Ce) , Beryllium Allanite (Ce), Gallium Allanite (Ce)
Abbreviation : Aln-Ce
literature
Dana, J. D., & Dana, E. S. (1892). The system of mineralogy of James Dwight Dana, 1837-1868: descriptive mineralogy . J. Wiley & sons.