Formula: (Ca,Na)2Nb2O6(OH,F)
Origin of name: from Greek for fire and green
Crystal system: cubic
Crystal class: 4/m -3 2/m
Twinning: rare by spinel law
Unit cell: a = 10.42 Å
Colour: yellowish brown, reddish brown, brown to black
Diaphaneity:
Luster: vitreous to resinous
Habit: crystals octahedral, to 1 cm, irregular masses, embedded grains
Hardness: 5 to 5.5
Specific gravity: 4.48
Cleavage: 1; {111} sometimes distinct, or parting
Tenacity: subconchoidal to uneven, brittle
Streak:
Synonyms/varieties:
Comments: series with microlite
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