Melanocerite-(Ce)

melanocerite-(Ce)

gadolinite

yttrialite-(Y)

fergusonite

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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

Pegmatites

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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