IIMORIITE

    Class : Silicates
    Subclass : Nesosilicates
    Crystal system : Triclinic
    Chemistry : Y2(SiO4)(CO3)
    Rarity : Very rare

Iimoriite is a yttrium silicate with a complex structure, which includes numerous CO3 groups. It is an extremely rare secondary mineral that is found in environments rich in rare earth elements, mainly pegmatites with rare earths and uranium, hyperalkaline granites with riebeckite and aegyrine and their pegmatites with amazonite - zinnwaldite. It was named in honor of the Japanese mineralogist Satoyasu Iimori of the Tokyo Institute of Physical and Chemical Research. Iimoriite forms small grains and masses of reduced size, not exceeding 3 cm, pale brown to pale purplish gray in color.

Main photo : Iimoriite of Trimouns, Luzenac, Ariège, France © Pascale & Daniel Journet

Iimoriite from Trimouns, Luzenac, Ariège, France © Vincent Bourgoin
Iimoriite from Trimouns, Luzenac, Ariège, France © Pascale & Daniel Journet
Iimoriite from Trimouns, Luzenac, Ariège, France © Yannick Vessely
Iimoriite from Suishoyama pegmatite, Fukushima, Japan © Toshinori Kobayashi

Iimoriite in the World

Iimoriite is known from Ploskogorskaya (Keivy Massif) as well as from some microcline pegmatites in Japan (Fusamata, Suishoyama) where it seems to derive from the alteration of thalenite-(Y).

Iimoriite in France

In France, iimoriite is present in pink to colorless crystals up to 1 cm in the hydrothermalized rare earth dolomites of Luzenac (Trimouns, Ariège).

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 5.5 to 6
Density : 4.47
Fracture : Underterminated
Streak : White

TP : Translucent to transparent
RI : 1.753 to 1.830
Birefringence : 0.077
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : NoneRadioactivity : None