Allanite-(Ce) – [(Ce,Y,Ca)2(Fe2+,Fe3+)Al2(SiO4)(Si2O7(O)(OH)]

Allanite-(Ce) is extremely rare at MSH.

PHYSICAL CHARACTERISTICS:

 

  • Color is usually beige to dark brown on the acicular crystals and
    varies from very deep red to dark brown on the tabular crystals.
  • Luster is vitreous on tabular crystals and dull to greasy on
    acicular crystals.
  • Diaphaneity is transparent to translucent on tabular crystals and
    opaque on acicular crystals.
  • Crystal System is monoclinic; P21/m.
  • Crystal Habits include sharp, thin tabular crystals to 4mm
    and aggregates of radiating individual crystals.
  • Cleavage {001} is imperfect and {100}{110} are poor.
  • Fracture is conchoidal to uneven.
  • Hardness is 5.5 – 6.
  • Specific Gravity is approximately 4.11 g/cm3.
  • Streak is gray.
  • Associated Minerals include calcite, chlorite group, dolomite and
    quartz.
  • Distinguishing Features: Crystal habit and color.
  • Origin: Named in 1810 after Thomas Allen (1777-1833), the Scottish
    mineralogist who first noticed it.

 

 

Dana class # 58.2.1a.1 – Sorosilicates; isolated tetrahedral noncyclic groups, N > 1; insular, mixed, single, and larger tetrahedral groups; epidote group
Strunz class # VIII/C.23-80 – Silicates; sorosilicates, mixed structure with [SiO4]2- and [Si2O7]6- groups; epidote group