Formula: (U,Ca,Ce)2(Nb,Ta)2O6(OH,F)
Origin of name: from uranium and pyrochlore
Crystal system: Cubic/Isometric, commonly metamict
Crystal class: 4/m 3 2/m
Twinning: Rarely on {111}
Unit cell: a = 10.44
Colour: Yellowish brown, red, reddish brown, amber, black
Diaphaneity: Translucent to opaque
Luster: Resinous
Habit: crystals octahedral, modified, massive
Hardness: 4 to 5
Specific gravity: 4.51-4.90
Cleavage: None
Tenacity: Brittle, subconchoidal fracture
Streak: Brownish yellow
Synonyms/varieties: Ellsworthite, hatchettolite
Comments: Radioactive
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