Mineral Information and Data:

Allanite-(La)
CaLaAl2Fe2+(Si2O7)(SiO4)O(OH) [CNMNC approved formula]

Named after the Scottish mineralogist, T. Allan (1777-1833) and the La content.

IMA status : Approved Species 2006 (IMA2003-065)
CLASSIFICATION 
Dana
(8th edition) :
58.02.01c.02  (This Dana# Added)
  (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 = 8.914 Å, b = 5.726 Å, c = 10.132 Å, b = 114.87°
Crystal Habit: Crystals tabular, long prismatic to acicular, commonly massive, bladed, or embedded grains.
Twinning: Common on {100}, polysynthetic
  
Color: Brown to black
Diaphaneity: Transparent to translucent
Luster: Vitreous, resinous to submetallic
Hardness (Mohs): 6
Measured Density: 3.93 g/cm3
Cleavage: Imperfect on {001}; poor on {100} and {110}.
Tenacity: Brittle
Fracture: Conchoidal to uneven
Streak: Grayish brown
  
Geologic Setting: Found in close association with calcite and barite in barite veins that cut a dolomitic metamorphosed limestone.
  

 

Allanite-(La)
Allanite-(La)
Origin: Wobarn, Western Australia, Australia
Sample size: unknown
Sample owner: Kennedy Mineral Collection, Carleton University
Photo: Steve Sorrell - Crocoite.com

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