Brown crystal aggregates of caryocerite (a variety of melanocerite-(Ce)) from the type locality for the mineral in Norway: Melanocerite type locality, Vestfold og Telemark, Norway. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Melanocerite-(Ce)
Melanocerite-(Ce) is an IMA-recognized mineral species in the silicate class, with the chemical formula Ce₅(SiO₄,BO₄)₃(OH,O).
It is a member of the Apatite structural group.
Key properties: Mohs hardness 5–6; specific gravity 4.13–4.29; Light brown streak; Resinous to greasy luster; optically uniaxial.
IMA symbol Mcrt-Ce, IMA status: questionable, named in 1887.
Found in nepheline syenite pegmatites (Langesundsfjord, Norway); in alkalic granite pegmatites (Russia).
It is found associated with Astrophyllite, ferrian biotite, leucophanite, fluorite (Langesundsfjord, Norway); gadolinite, yttrialite, fergusonite (Russia).
Its name comes from the Greek for black or dark and cerium in its composition.