Mineral Information and Data:

Allanite-(Ce)  
CaCeFe2+Al2(Si2O7)(SiO4)O(OH) [CNMNC approved formula]

Named after the Scottish mineralogist, T. Allan (1777-1833) who discovered the species.

IMA status : Approved Species 1987 ()
CLASSIFICATION 
Dana
(8th edition) :
58.02.01c.01  (This Dana# Changed)
  (58) Sorosilicate Insular, Mixed, Single, and Larger Tetrahedral Groups
  (58.02) with cations in [6] and higher coordination; single and double groups (n=1,2)
  (58.02.01c) Epidote group (Allanite subgroup)
  
Nickel-Strunz
(10th edition) :
09.BG.05b
  (09) Silicates
  (09.B) Sorosilicates (dimer) structures
  (09.BG) Sorosilicates with mixed SiO4 and Si2O7 groups; cations in octahedral [6] and greater coordination
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 8.93 Å, b = 5.77 Å, c = 10.16 Å, b = 114.7°
Crystal Habit: Crystals tabular, long prismatic to acicular, commonly massive, bladed, or embedded grains.
Twinning: Common on {100}, polysynthetic
  
Color: Brown to black
Diaphaneity: Translucent to opaque
Luster: Vitreous, resinous to submetallic
Hardness (Mohs): 5.5 to 6
Measured Density: 3.5 - 4.2 g/cm3
Cleavage: Imperfect on {001}; poor on {100} and {110}.
Tenacity: Brittle
Fracture: Conchoidal to uneven
Streak: Gray, grayish brown
  
Geologic Setting: An accessory in some granites and granite pegmatites, syenites, more rarely in gabbroic pegmatites. Rarely in schists, gneisses, and some contact metamorphosed limestones; a clastic component of sediments.
Mineral Association: Epidote, muscovite, fluorite
  
Other Properties: Radioactive. Gemstone Unlikely Available.
Comments: Dana Number Changed from 58.2.1a.1

 

Allanite-(Ce)
Allanite-(Ce) and smoky quartz in pegmatite matrix
Origin: Capitan, New Mexico, U.S.A.
Sample size: 9 x 6 x 5 cm,
allanite crystals to 1.2 cm, smoky quartz to 1.5 cm
Photo: Tom Loomis

 

Allanite-(Ce)
(zoom-in of above)

 

Allanite-(Ce)
(zoom-in of above)

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