Formula: ThO2
Origin of name: From composition containing thorium
Crystal system: Isometric/cubic
Crystal class: 4/m 3 2/m
Twinning: On {111} interpenetrant
Unit cell: a = 5.595 Å
Colour: Black, brownish black, dark gray, dark reddish brown, may have a bronzy tarnish
Diaphaneity: Opaque, transparent in very thin fragments
Luster: Submetallic when fresh, altering to resinous or hornlike
Habit: crystals cubic or cubo-octahedral, embedded crystals or grains
Hardness: 6.5 to 7
Specific gravity: 9.7-9.8
Cleavage: 1; {001} poor
Tenacity: Brittle, conchoidal to uneven fracture
Streak: Gray to greenish gray
Synonyms/varieties: Aldanite (U,Pb-rich variety)
Comments: Series with uraninite. Radioactive, diamagnetic
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