Mineral Information and Data:

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

Named in 1906 as priorite; renamed in 1906 (IMA) 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; 1966 ()
(8th edition) :  
  (08) Multiple Oxides with Nb, Ta, and Ti
  (08.03) where A (B2O6)
  (08.03.06) Aeschynite group
(10th edition) :
  (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 = 7.44–7.50 Å , b = 10.92–11.04 Å, c = 5.18 Å
Crystal Habit: Crystals, to 10 cm, commonly tabular, less commonly prismatic, forms {001}, {010}, {021}, {110}, {210}, {111}; granular.
Color: Pale yellow, yellow-orange, pale greenish yellow
Diaphaneity: Semitransparent
Luster: Submetallic to pearly on crystal faces, resinous to waxy on fracture surfaces
Hardness (Mohs): 5 - 6
Measured Density: 4.82–4.93 g/cm3
Cleavage: Perfect on {100}, {010}, and {001}
Tenacity: Brittle
Fracture: Uneven
Streak: White, pale yellow, reddish yellow
Polymorphism and Series: Forms two series, with aeschynite-(Ce) and with tantalaeschynite-(Y)
Geologic Setting: In granite and granite pegmatites; in ankerite-dolomitic carbonatites; as a detrital mineral in placers.
Mineral Association: Euxenite, monazite, xenotime, allanite, zircon, fergusonite, thorite, synchysite, gadolinite, chernovite, columbite, biotite, muscovite, titanite, corundum
Synonyms/varieties: Aeschinite-(Y), Aeschynite-(Yt), Blomstrandine, Blomstrandinite, Priorite Taiyite


1 mm tabular crystal of aechynite-(Y) crystal
on matrix of albite, quartz and muscovite.
Origin: Val. Pellice, Piedmont, Italy
Sample size: 5 x 2.7 cm
Photo: John Veevaert, Trinity Mineral Co


(zoom-in of above)