Mineral Information and Data:

Aeschynite-(Ce)  
(Ce,Ca,Fe,Th)(Ti,Nb)2(O,OH)6 [CNMNC approved formula]

Named in 1828 for its composition and from the Greek for "shame," in allusion to the inability of chemists, at the time of its discovery, to separate some of its constituents.

IMA status : Renamed IMA Approved; 1987 ()
CLASSIFICATION 
Dana
(8th edition) :
08.03.06.01  
  (08) Multiple Oxides with Nb, Ta, and Ti
  (08.03) where A (B2O6)
  (08.03.06) Aeschynite group
  
Nickel-Strunz
(10th edition) :
04.DF.05
  (04) Oxides and Hydroxides
  (04.D) Metal:Oxygen = 1:2 and similar
  (04.DF) With large (+- medium-sized) cations; dimers and trimers of edgesharing octahedra
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 7.54 Å , b = 10.96 Å, c = 5.40 Å
Crystal Habit: Crystals, prismatic acicular or tabular; massive
  
Color: Black, brownish black, brown, brownsih yellow
Diaphaneity: Subtranslucent
Luster: Submetallic, resinous to waxy; dull when altered.
Hardness (Mohs): 5 - 6
Measured Density: 4.96 to 5.2 g/cm3
Cleavage: 2;{100} interrupted, parallel (010) parting, when not metamict
Tenacity: Brittle
Fracture: Conchoidal
Streak: Yellow, dark brown to black
  
Polymorphism and Series: Dimorphous with lucasite-(Ce); forms series with nioboaeschynite-(Ce) and with aeschynite-(Y).
Geologic Setting: In nepheline syenites and alkali syenite massifs; in granite pegmatites; in carbonatites in alkalic rocks; a detrital mineral in placers.
Mineral Association: Feldspar, zircon, samarskite, columbite, allanite, titanite
  
Other Properties: Radioactive. Gemstone Extremely Rare.
Comments: Three distinct species with the extensions -Ce, -Nd, and -Y indicating the predominant rare earth cation in the formula.

 

Aeschynite-(Ce)
Origin: Frigstad, Iveland, Norway, Europe
Sample size: 1.3 x 1 x 0.7 cm
Photo: John Veevaert, Trinity Mineral Co

 

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

 

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

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