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Formula: Ce5(SiO4,BO4)3(OH,O)
Nesosilicate, borosilicate,
cerium-bearing mineral
Crystal System: Hexagonal
Specific gravity: 4.13 to 4.30 measured
Hardness: 5 to 6
Streak: Pale brown
Colour: Brown to black
Solubility: Soluble in 1:1 hydrochloric acid leaving a solica residue, and also soluble in concentrated sulphuric
acid (Dana)
Common impurities: Th
Weakly RADIOACTIVE
Environments
Melanocerite-(Ce) is generally metamict. Sometimes it alters to
bastnäsite
(Dana).
Localities
At the type locality, Melanocerite type locality, Kjeøya, Barkevik area, Langesundsfjorden, Larvik, Vestfold og
Telemark, Norway, melanocerite-(Ce) occurs as deep brown to black platy crystals, from a few mm to about
2 cm in size, embedded in feldspar in a
nepheline syenite
pegmatite. Associated minerals include
astrophyllite, ferrian
biotite, leucophanite and
fluorite
(HOM, Mindat).
At the Burpala alkaline massif, Maigunda River, Mama River Basin, Buryatia, Russia, melanocerite-(Ce) occurs
in alkalic granite
pegmatites, associated with
gadolinite,
yttrialite-(Y) and
fergusonite
(HOM).
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