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Formula: (Ca,REE)4Ce2Al☐2(B4Si4O22)(OH)2
Inosilicate (chain silicate), hellandite group,
cerium- and boron- bearing mineral
Crystal System: Monoclinic
Hardness: 5½ to 6
Colour: Light green
Weakly RADIOACTIVE
Environments
Localities
At the type locality, Campo Padella, Capranica, Viterbo Province, Lazio, Italy, transparent, light-green coloured,
crystals of hellandite-(Ce) up to 0.4 mm in size have been found in miarolytic cavities. It is also found in the
ground-mass of volcanic ejectum filling voids and fractures in the rock and systematically intergrown with
britholite. Other associated minerals include
vonsenite, helvine and
baddeleyite
(Mindat).
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