Outstanding dissakisite-(Ce) crystals from this famous French locality for rare earth minerals: Trimouns, Luzenac, Midi-Pyrénées, France. Very nice under the microscope for the contrast with the matrix. — Photo: David Hospital · CC BY-SA 4.0
Dissakisite-(Ce)
Dissakisite-(Ce) is an IMA-recognized mineral species in the silicate class, with the chemical formula CaCe(Al₂Mg)[Si₂O₇][SiO₄]O(OH).
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Epidote, allanite structural group.
Key properties: specific gravity 3.75; Vitreous luster; optically biaxial.
IMA symbol Dis-Ce, IMA status: approved, named in 1990.
Formed in marble, under amphibolite-facies metamorphism, at about 600 ± C and 7 kbar (Balchen Mountain, Antarctica).
It is found associated with Calcite, dolomite, forsterite, clinohumite, phlogopite, chlorite, ilmenite-geikelite, spinel, zircon, pyrrhotite (Balchen Mountain, Antarctica).
Its name comes from the Greek for twice over, for a magnesium analog of allanite being described twice.